NASDAQ: PCVX

We carefully select our target disease areas and vaccine candidates based on the following criteria: areas of significant unmet medical need, clear commercial opportunity and efficient market adoption, acceptable biological risk and established or acceptable clinical pathways. We are leveraging our scalable cell-free protein synthesis platform to develop potentially superior and novel conjugate and protein vaccine candidates for adult and pediatric indications using these criteria.

Our pipeline includes:

•PCV candidates that we believe are among the broadest-spectrum PCV candidates currently in development, targeting the approximately $8 billion global pneumococcal vaccine market. Pneumococcal disease ("PD") is an infection caused by Streptococcus pneumoniae bacteria. It can result in invasive pneumococcal disease (“IPD”), including meningitis and bacteremia, and non-invasive PD, including pneumonia, otitis media and sinusitis. Our broad-spectrum, carrier-sparing PCV candidates, VAX-31, VAX-24 and VAX-XL, are designed to improve upon standard-of-care PCVs for both adults and children by covering the serotypes that are responsible for increasing portions of IPD in circulation and are associated with high case-fatality rates, antibiotic resistance and meningitis, while maintaining coverage of previously circulating strains that are currently contained through continued vaccination.

◦PCV Franchise Adult Indication:

▪VAX-31 is a 31-valent, broad-spectrum, carrier-sparing investigational PCV being developed for the prevention of IPD and pneumonia. VAX-31 is the broadest-spectrum PCV in the clinic, and has the potential to provide protection against both currently circulating and historically prevalent serotypes. VAX-31 was designed to increase coverage, in a single vaccine, to approximately 95% of IPD and approximately 88% of pneumococcal pneumonia circulating in adults in the United States aged 50 and older, with the potential to provide an incremental 14-34% of coverage for IPD and an incremental 19-31% of coverage for pneumococcal pneumonia over current standard-of-care adult PCVs.

•In September 2024, we announced positive topline results from a Phase 1/2 study of VAX-31 in adults. The VAX-31 Phase 1/2 clinical study was a randomized, observer-blind, active-controlled, dose-finding clinical study designed to evaluate the safety, tolerability and immunogenicity of a single injection of VAX-31 at three dose levels (Low, Middle and High) and compared to Prevnar 20® ("PCV20") in 1,015 healthy adults aged 50 and older. In the Low, Middle and High Doses, all serotypes were dosed at 1.1mcg, 2.2mcg and 3.3mcg, respectively, except serotypes 1, 5 and 22F, which were dosed at 1.65mcg, 3.3mcg, and 4.4mcg, respectively. The Phase 1 portion of the study included 64 healthy adults 50 to 64 years of age and the Phase 2 portion included

951 healthy adults 50 years of age and older. The immunogenicity objectives of the study included an assessment of the induction of antibody responses at Month 1, based on opsonophagocytic activity (“OPA”) and immunoglobulin G ("IgG"), at each of the three VAX-31 doses and compared to PCV20 for the 20 serotypes in common, as well as for the additional 11 serotypes contained in VAX-31, but not in PCV20.

In the Phase 1/2 study, VAX-31 was observed to be well tolerated and demonstrated a safety profile at all doses studied through the full six-month evaluation period similar to PCV20. VAX-31 showed robust OPA immune responses for all 31 serotypes at all doses studied. At the Middle and High Doses, VAX-31 met or exceeded the regulatory immunogenicity criteria for all 31 serotypes and, at the Low Dose, for 29 of 31 serotypes. At the VAX-31 High Dose, average OPA immune responses were greater for 18 of 20 serotypes compared to PCV20 (geometric mean ratio (“GMR”) greater than 1.0), with seven of these serotypes achieving statistically higher immune responses compared to PCV20. At the Middle Dose, 13 of 20 serotypes had a GMR greater than 1.0 and five serotypes achieved statistically higher immune responses compared to PCV20. At the Low Dose, 18 of 20 serotypes met the OPA response non-inferiority criteria, 8 of 20 serotypes had a GMR greater than 1.0 and three serotypes achieved statistically higher immune responses. For all 11 incremental serotypes unique to VAX-31, and not in PCV20, all three doses met the superiority criteria.

Based on these positive results, we selected the High Dose of VAX-31 to advance to an adult Phase 3 program.

•In November 2024, we announced that the FDA granted breakthrough therapy designation ("BTD") for VAX-31 for the prevention of IPD in adults and, in August 2025, we announced that the FDA expanded the BTD for VAX-31 to include the prevention of pneumonia caused by Streptococcus pneumoniae.

•In December 2025, following an FDA End-of-Phase 2 meeting, we announced that the first participants were dosed in a Phase 3 pivotal, non-inferiority trial evaluating VAX-31 for the prevention of IPD and pneumonia in adults compared to standard-of-care PCVs ("OPUS-1"). We expect to announce topline safety, tolerability and immunogenicity data from this study in the fourth quarter of 2026.

•In January 2026, we announced the initiation of an additional Phase 3 trial evaluating VAX-31 when administered concomitantly with a licensed, high-dose seasonal influenza vaccine in pneumococcal-naïve adults aged 50 years and older (“OPUS-2”). In February 2026, we announced the initiation of a separate Phase 3 study evaluating VAX-31 in adults previously vaccinated with a lower-valency pneumococcal vaccine (“OPUS-3”). We expect to report safety, tolerability and immunogenicity data from the OPUS-2 and OPUS-3 studies in the first half of 2027. We are also planning for a manufacturing consistency study (e.g., a lot-to-lot study).

◦PCV Franchise Pediatric Indication:

▪VAX-31 is a 31-valent, broad-spectrum, carrier-sparing investigational PCV also being developed for the prevention of IPD in children. VAX-31 is the broadest-spectrum PCV in the clinic designed to cover approximately 92% of IPD in U.S. children under five years of age and approximately 96% of otitis media due to Streptococcus pneumoniae in U.S. children five years of age or under.

▪In December 2024, we announced that the first participants were dosed in the first stage of a Phase 2, randomized, dose-finding study of VAX-31 in infants. Stage 1 of the study evaluated the safety and tolerability of VAX-31 at three dose levels (Low, Middle and High) and compared to PCV20 in 48 infants in a dose-escalation approach. In the Low, Middle and High Doses, all serotypes were dosed at 1.1mcg, 2.2mcg and 3.3mcg, respectively, except serotypes 1, 5 and 22F, which were dosed at 1.65mcg,

3.3mcg, and 4.4mcg, respectively. Participants who received VAX-31 in Stage 1 continued the standard dosing regimen as part of Stage 2.

▪In February 2025, we announced that the Phase 2, randomized, dose-finding study of VAX-31 in healthy infants had advanced to the second stage of the study. Stage 2 of the study is evaluating the safety, tolerability and immunogenicity of VAX-31 at the same three dose levels evaluated in Stage 1 and compared to PCV20. In line with recommendations from the ACIP, the study design includes a primary immunization series consisting of three doses given at two months, four months and six months of age, followed by a subsequent booster dose at 12-15 months of age.

▪In September 2025, we announced advancement of the VAX-31 infant Phase 2 randomized, dose-finding study to the third and final stage following modifications to the protocol to add a new dose arm to evaluate a VAX-31 Optimized Dose (majority of serotypes dosed at 4.4mcg and the balance dosed at 3.3mcg) and discontinue enrollment in the Low Dose arm. The Middle and High Dose arms continued as planned.

▪The modified study is evaluating the safety, tolerability and immunogenicity of VAX-31 and compared to PCV20 in 900 participants, including the 100 participants previously enrolled in the Low Dose arm.

▪In January 2026, we announced that we completed enrollment of this study. We expect to announce topline safety, tolerability and immunogenicity data from the primary three-dose immunization series and booster dose either sequentially or together by the end of the first half of 2027.

▪Pending the VAX-31 Phase 2 infant study readout, we plan to initiate a Phase 3 program in infants with an Optimized Dose formulation of VAX-24 or VAX-31.

▪VAX-24 is a 24-valent, broad-spectrum, carrier-sparing investigational PCV being developed for the prevention of IPD in infants, and it covers more serotypes than any pneumococcal infant vaccine on the market today.

•In March 2025, we announced positive topline, interim data from the VAX-24 infant Phase 2 study, a randomized, observer-blind, dose-finding two-stage clinical study evaluating the safety, tolerability and immunogenicity of VAX-24 in healthy infants that enrolled 803 participants.

•In November 2025, we announced final safety, tolerability, and immunogenicity results from the VAX-24 infant Phase 2 study that were consistent with the positive interim data reported in March 2025 and showed that VAX-24 elicited robust, dose-dependent immune responses, with little to no evidence of carrier suppression observed. The final data analysis included full 6-month safety results and complete post-dose 3 (primary immunization series) and post-dose 4 (booster dose) IgG and OPA results. The key immunogenicity endpoints included an assessment of immune responses for each of the VAX-24 dose levels (Low, Mid, Mixed) in comparison with PCV20 for the 20 common and 4 unique serotypes in VAX-24. At 1-month post-dose 3 and post-dose 4, immune responses were assessed based on serotype-specific IgG seroconversion rates (IgG threshold value of ≥0.35mcg/mL). IgG GMRs were also assessed at 1-month post-dose 3 and post-dose 4, along with other key immunogenicity endpoints, including OPA.

In this study, VAX-24 was well-tolerated and demonstrated a safety profile similar to PCV20 across all doses studied. Post-dose 3 and post-dose 4, all VAX-24 doses evaluated demonstrated robust IgG and OPA immunogenicity responses.

•Post-dose 3, all VAX-24 doses met target precedent Phase 2 non-inferiority criteria on relative seroconversion rates (lower limit of the 95% confidence interval for the difference between the proportion of participants achieving the pre-defined seroconversion rate (IgG concentration ≥0.35 mcg/mL) is > -15% for each serotype) for the highest circulating serotypes, as defined by the

percentage of IPD caused in individuals <5 yrs of age in the U.S. in 2023 based on the U.S. Center for Disease Control ("CDC") active bacterial core ("ABC") surveillance data, contained in VAX-24. The Low and Mid doses met the seroconversion rate criteria for 20 of 24 serotypes overall and the Mixed Dose met such criteria for 19 of 24 serotypes. The Mid and Mixed Doses met the target Phase 2 IgG GMR point estimate of >0.6 for 21 of 24 serotypes.

•Post-dose 4, all VAX-24 doses met our target Phase 2 IgG GMR point estimate of >0.6 for the three highest circulating serotypes contained in VAX-24. The Mixed Dose met this target for 19 of 24 serotypes overall and the Mid dose met this target for 18 of 24 serotypes. Post-dose 4, VAX-24 elicited robust memory responses across all doses for all serotypes.

•Additionally, the four incremental serotypes unique to VAX-24 that provide expanded serotype coverage relative to PCV20 elicited robust immune responses and met all target criteria across all endpoints at all doses evaluated.

•The final positive data from the VAX-24 infant Phase 2 dose-finding study further validated our rationale for exploring higher doses in the ongoing VAX-31 infant Phase 2 study.

◦VAX-XL is a third-generation PCV candidate designed to provide the broadest coverage of any PCV currently in development.

•VAX-A1, a novel conjugate vaccine candidate designed to prevent disease caused by Group A Streptococcus (“Group A Strep”). Group A Strep is pervasive globally and causes an estimated 800 million cases of illness annually, including pharyngitis, or strep throat, and certain severe invasive infections and sequelae. There is currently no vaccine against Group A Strep, which is one of the leading infectious disease-related causes of death and disability worldwide and a significant contributor to the prescription of antibiotics in children. We believe we have demonstrated preclinical proof of concept for VAX-A1, the data for which were published in December 2020. We plan to initiate a Phase 1 adult study for VAX-A1 in 2026, with the primary objective of assessing safety and tolerability.

•VAX-GI, a novel preclinical vaccine candidate being developed as a preventative treatment for dysentery and shigellosis, which is caused by Shigella bacteria. Shigella is a bacterial illness estimated to cause 80 million to 165 million cases of disease and 600,000 deaths annually, mostly among children. The central antigen in VAX-GI is IpaB, a well-appreciated antigen that other developers have been unable to produce in an amount sufficient to enable a commercial product. With our cell-free technology, we believe we can produce this antigen at substantially improved yields, allowing for commercial-scale production. VAX-GI is being developed in collaboration with the University of Maryland, Baltimore as well as with partial funding from two research grants awarded by the National Institutes of Health (“NIH”). As part of our continued focus on strategic capital deployment and in order to prioritize our resources towards our PCV franchise, we announced in August 2025 that we had paused the advancement, beyond preclinical development, of VAX-GI while remaining confident in its potential and preserving the option to advance the program in the future.

•Other discovery-stage programs that leverage our cell-free protein synthesis platform, which, if proven successful in preclinical studies, could also be advanced into IND-enabling activities and clinical studies.

Our Approach

To address areas of significant unmet medical need, we carefully select the disease areas we target and are developing vaccine candidates based on the following criteria:

•Clear commercial opportunity and efficient market adoption: We select vaccine targets that are characterized by an established patient population and significant unmet medical need. Our PCV candidates are designed to improve upon the standard-of-care for both adults and children by covering the serotypes that are responsible for a significant portion of IPD in circulation and are associated with high case-fatality rates, antibiotic resistance and meningitis, while maintaining coverage of previously circulating strains that are currently contained through continued vaccination practice. We believe that by providing the broadest coverage of serotypes for PCVs, as well as providing novel vaccines for diseases for which there are no currently approved vaccines, we can leverage the

U.S. Centers for Disease Control (“CDC”), ACIP and similar international advisory body recommendations to drive rapid and significant market adoption.

•Acceptable biological risk: We choose vaccine targets with well-understood mechanisms of action and strong precedents for positive preclinical study results that we believe will translate to positive clinical trial results. For example, conjugate vaccines have demonstrated effectiveness in both preclinical and clinical trials against a range of bacteria, including Streptococcus pneumoniae, meningococcus and haemophilus influenza B. There is consistent evidence that antibodies directed against these bacteria are protective against their respective diseases.

•Established or acceptable clinical pathways: We pursue vaccine targets that we believe have established or acceptable clinical development pathways in order to accelerate the potential time to market. For example, we believe that our PCVs would receive regulatory approval based on successful completion of clinical studies utilizing well-defined surrogate immune endpoints, consistent with how other PCVs have obtained regulatory approval in the past, rather than requiring clinical field efficacy studies. For our novel vaccine candidates, for which we believe clinical field efficacy studies will be necessary, we select disease areas with high attack rates, such as Group A Strep, which may allow for more manageable study sizes.

Our Platform

Our modern synthetic techniques, including advanced chemistry and the XpressCF™ cell-free protein synthesis platform, offer several advantages over conventional cell-based protein expression methods, which we believe enable us to generate superior, novel, broader-spectrum and/or more immunogenic vaccines. In the context of conjugate vaccines, we believe we can add more antigenic strains without compromising the overall immune response. In particular, our ability to specify the attachment point of antigens, including polysaccharides, on protein carriers represents a significant improvement over the random conjugation that occurs with conventional technologies. This site-specific conjugation is designed to ensure that B-cell and/or T-cell epitopes are optimally exposed, maximizing the immune response, whereas random conjugation blocks these critical immunogenic epitopes, which dampens the immune response and may lead to a phenomenon known as carrier suppression.

We believe this precise control of conjugation chemistry enables us to design broader-spectrum conjugate vaccine candidates using carrier-sparing conjugates that use less protein carrier without sacrificing immunogenicity. We are also able to design novel conjugate vaccine candidates using standard amounts of protein carrier to generate heightened immunogenicity. Beyond conjugate vaccines, we believe we can also design novel protein vaccine candidates based on well-appreciated but highly complex antigens that currently cannot be made using conventional technologies to address diseases for which there are no available vaccines. In addition, our platform enables us to rapidly screen vaccine candidates, requiring less effort than conventional chemistry which allows us to produce and iterate conjugate candidates, thereby dramatically accelerating the development cycle of designing, producing and testing vaccine candidates.

We are re-engineering the way highly complex vaccines are made to develop potentially superior and novel conjugate and protein vaccine candidates for adult and pediatric indications using the above criteria by taking advantage of the following:

•Site-specific conjugation. We are able to specify the attachment point of antigens, including polysaccharides, on protein carriers to ensure optimal exposure of B-cell and/or T-cell epitopes, thereby creating protein carriers designed to have enhanced potency. We believe this precise control of conjugation chemistry enables us to create broader-spectrum conjugate vaccine candidates using carrier-sparing conjugates that use less protein carrier without sacrificing immunogenicity. We are also able to design novel conjugate vaccine candidates using standard amounts of protein carrier to generate heightened immunogenicity.

•Production of novel protein vaccines. We can design novel protein vaccine candidates based on well-appreciated but highly complex antigens that currently cannot be made with conventional technologies to address diseases for which there are no available vaccines, and we believe we may be able to leverage our platform to rapidly respond to new or emerging pathogens. We can design and produce these “tough-to-make” antigens that conform to the target pathogens, thereby increasing the likelihood that the vaccine will elicit a protective immune response.

•Speed, flexibility and scalability of the discovery engine. We are able to rapidly screen vaccine candidates and produce conjugates, thereby accelerating the process of making and testing vaccine candidates. Because cell viability is not required for cell-free protein synthesis, we can utilize a broader range of reaction conditions as we seek to optimize proteins. This flexibility enables us to develop novel vaccine candidates unachievable with current technologies. Furthermore, we believe our platform can scale linearly from discovery to commercial scale.

Our Strategy

Our goal is to become a leader in the vaccines industry by using our cell-free protein synthesis platform to develop superior and/or novel vaccines to prevent or treat serious infectious diseases. Key elements of our strategy include:

•Advance our PCV candidates through clinical development and regulatory approval. Our PCV candidates, VAX-31,VAX-24 and VAX-XL, target the pneumococcal vaccine market. We are advancing these PCV candidates along a well-understood clinical development pathway in an effort to obtain regulatory approval in adults and infants based on successful completion of clinical studies using previously established surrogate immune endpoints, without the need to conduct clinical field efficacy studies, consistent with how other conjugate vaccines have obtained approval.

•Establish scalable production of our PCV candidates. We believe high-quality and scalable manufacturing is critical to our long-term success. We have designed and developed a proprietary, scalable and portable manufacturing process that we have scaled to supply clinical volumes and believe can scale to supply initial volumes of VAX-31 needed to support commercial launch. We have access to substantial manufacturing resources through our contract manufacturer, Lonza, that we believe can facilitate an independent path to market. For the adult indication, we are conducting scale-up activities to support potential regulatory approval and commercial launch of VAX-31 in this population using existing Lonza infrastructure. In October 2023, to complement this plan, we entered into a new commercial manufacturing agreement with Lonza to support the potential global commercialization of our PCV candidates in both the adult and pediatric populations. In November 2023, we entered into a manufacturing rights agreement with Sutro Biopharma, Inc ("Sutro Biopharma") to obtain control over the development and manufacture of cell-free extract, a key component of our PCV franchise. Pursuant to the manufacturing rights agreement, we obtained exclusive rights to independently, or through certain third parties, develop, improve and manufacture cell-free extract for use in connection with our vaccine candidates. In addition, in September 2025, we announced a new agreement with Patheon Manufacturing Services, LLC, part of Thermo Fisher Scientific (collectively, "Thermo Fisher") to provide custom commercial fill-finish capacity for our broad-spectrum PCVs at Thermo Fisher's Greenville, North Carolina facility. The initiative, which includes both manufacturing and related services, represents a long-term U.S. commercial manufacturing commitment of up to $1 billion.

•Create a long-lasting PCV franchise by offering the broadest-spectrum PCV available. The two leading pneumococcal vaccine franchises to date, Prevnar and Pneumovax 23 (“PPSV23”), have been administered well over a billion times, generating over $100 billion in combined sales over 20 and 40 years, respectively, and can attribute their success to having been the broadest-spectrum vaccines on the market. In addition, the recently approved PCV, Capvaxive® ("PCV21"), is now commercially available for the adult market. If approved, we believe VAX-31 and/or VAX-24 may potentially replace the standard-of-care PCVs currently available because of their coverage against both currently circulating and historically prevalent strains. We designed VAX-24 to address the 24 pneumococcal strains covered by Prevnar and PPSV23 that drive a significant portion of pneumococcal disease today with the durable, boostable immune response of a conjugate vaccine. Further, we have designed VAX-31 to address these 24 strains plus seven additional epidemiologically significant emerging strains that are causing increasing pneumococcal disease and antibiotic resistance, which collectively drive most pneumococcal disease today. With these broad-spectrum vaccine candidates, we believe we are well-positioned to obtain ACIP recommendations and potentially replace the current standard-of-care for pneumococcal disease prevention in both adult and pediatric populations, thereby creating a long-lasting PCV franchise.

•Develop novel vaccine candidates and leverage our platform to expand our pipeline.

◦ VAX-A1: We believe our data published in December 2020 demonstrated preclinical proof of concept for VAX-A1. We nominated the final vaccine candidate and initiated IND-enabling activities for VAX-A1 in 2021. We plan to initiate a Phase 1 adult clinical study in 2026, with the primary objective of assessing safety and tolerability.

◦VAX-GI: VAX-GI is being developed in collaboration with the University of Maryland, Baltimore as well as with partial funding from two research grants awarded by the NIH. We are in the process of identifying additional antigens to include with IpaB and engaged in early-stage process development activities. As part of our continued focus on strategic capital deployment and in order to prioritize our resources towards our PCV franchise, we announced in August 2025 that we had paused the advancement, beyond preclinical development, of VAX-GI while remaining confident in its potential and preserving the option to advance the program in the future.

◦Leverage our platform for other discovery stage programs. We are also able to leverage our platform as a discovery engine given our ability to uniquely create building blocks to construct potential novel conjugate and protein vaccine candidates, and we have other discovery-stage programs which leverage this platform.

•Continue to build a robust intellectual property portfolio. We have developed and are continuing to develop a comprehensive intellectual property portfolio related to vaccine applications, including manufacturing, formulation and process applications as well as protection for our specific vaccine candidates. We have rights to a robust portfolio of patents and patent applications related to the XpressCF platform through our exclusive license from Sutro Biopharma. We currently have four issued U.S. patents, two issued European patents and multiple issued patents internationally, and multiple pending patent applications in the United States and internationally that cover our vaccine candidates including vaccine formulations, protein-antigen conjugates, methods of making conjugate vaccines with various protein-antigen conjugates and other processes related to vaccine production, enhancements of immunogenicity and methods of use.

Our Pipeline

We have utilized our cell-free protein synthesis platform to generate a pipeline of vaccine candidates that we believe, if approved, may offer important advantages over existing vaccines or for which there are no vaccines available today. The following table summarizes our current pipeline:

Global Vaccine Market

The global vaccine market size is projected to reach $115.77 billion by 2033 from an estimated $72.75 billion in 2025, growing at a compounded annual growth rate of 5.78% from 2026 to 2033. The Prevnar franchise from Pfizer Inc. (“Pfizer”), comprised of Prevnar 13 (“PCV13”) and PCV20, was among the highest selling vaccine products in the world in 2025, accounting for an estimated 9% of global vaccine sales.

The pediatric vaccine market is large and well-established in the United States, European Union and many other countries around the world. The annual new birth cohort, which in North America and Europe approached approximately 10 million in 2024, drives ongoing sales year after year due to the recommended immunization schedules. In the United States, once a new vaccine is approved by the FDA, the ACIP considers whether to recommend the use of the vaccine. New pediatric vaccine classes that receive a recommendation from ACIP and/or government health and professional medical organizations are widely adopted by pediatricians and parents and are required by many schools, contributing to a national immunization rate for the diseases targeted by such vaccines of approximately 90%. It is estimated that vaccination in children born between 1994 and 2023 in the United States will result in net savings of $540 billion in direct costs and $2.7 trillion in societal costs, making them one of the most cost-effective public health interventions.

In addition, the adult vaccine market is undergoing rapid growth. Vaccination rates among adults have historically been lower relative to infants and vary by disease, though strong initiatives are underway to increase awareness and utilization.

Excluding the impact of the COVID-19 pandemic, studies estimate that tens of thousands of adults in the United States die annually of vaccine-preventable diseases, and hundreds of thousands more are hospitalized. Vaccine-preventable diseases among adults cost the U.S. economy an estimated $27 billion annually in direct and indirect expenses. In recent years, manufacturers have started developing more vaccines for the adult market, including Pfizer’s PCV13 and PCV20, Merck & Co., Inc.'s (“Merck”) PCV15 and PCV21, GSK plc's (“GSK”) Shingrix and multiple vaccines to prevent respiratory syncytial virus ("RSV"). The U.S. adult pneumococcal market generated estimated annual sales of more than $1.5 billion in 2025, and Shingrix, a vaccine for shingles (herpes zoster), debuted with over $1 billion in sales in 2018 as it replaced Merck’s incumbent vaccine, Zostavax, after receiving an ACIP preferred recommendation, and generated over $4.8 billion in global sales in 2025. The vaccines to prevent RSV from Pfizer and GSK that were approved by the FDA in May 2023, and from Moderna that was approved by the FDA in May 2024, generated approximately $1.8 billion in global sales in 2025.

In October 2024, the ACIP voted to recommend expanding the age-based pneumococcal vaccination guidelines for pneumococcal vaccination in adults to begin at 50 years of age and older from the prior recommendation beginning at 65 years of age and older, which expanded the market by adding approximately 62 million additional eligible Americans for the universal recommendation.

Pneumococcal Disease

Pneumococcal disease is an infection caused by Streptococcus pneumoniae bacteria. It can result in IPD, including meningitis and bacteremia, and non-invasive pneumococcal disease, including pneumonia, otitis media and sinusitis. Global pneumococcal disease in children is driven by emerging serotypes not covered by currently available vaccines and in adults by not only emerging serotypes, but also fragmented coverage of today's standard-of-care vaccines. In the United States, pneumococcal pneumonia is estimated to result in approximately 225,000 U.S. adult hospitalizations each year. Streptococcus pneumoniae is among the WHO’s top antibiotic-resistant pathogens to be urgently addressed, and the United States CDC lists drug-resistant Streptococcus pneumoniae as a “serious threat.” In children under five, Streptococcus pneumoniae is the leading cause of vaccine-preventable deaths globally, resulting in approximately 300,000 deaths annually. It is estimated that acute otitis media affects approximately 5 million children and results in greater than 10 million antibiotic prescriptions annually in the United States. Pneumococci also cause over 50% of all cases of bacterial meningitis in the United States. Antibiotics are used to treat pneumococcal disease, but some strains of the bacteria have developed resistance to treatments. The morbidity and mortality due to pneumococcal disease are significant, particularly for young children and older adults, underscoring the need for a broader-spectrum vaccine.

Evolution of Pneumococcal Vaccines

There are currently two types of vaccines targeting pneumococcal disease—polysaccharide-only vaccines and PCVs. Polysaccharide vaccines contain polysaccharide antigens, which induce antibodies (B-cell responses) that bind to a bacteria’s outer coating of polysaccharides and clear the bacteria. PCVs improve on polysaccharide vaccines by attaching, or conjugating, the polysaccharide antigen to a non-disease specific protein carrier. PCVs induce both an improved B-cell response and a T-cell response, resulting in a stronger and more durable immune response and longer-lasting protection, as compared to polysaccharide vaccines, which only induce a B-cell response.

Pneumococcal Polysaccharide-Only Vaccines

PPSV23, manufactured and marketed by Merck is the only pneumococcal polysaccharide vaccine widely available. PPSV23 is indicated for the prevention of pneumococcal disease in adults and was first approved in the United States in 1977, at which time it contained 14 different strains of pneumococcal bacteria. In 1983, it was replaced by the current version containing 23 different strains. PPSV23 is routinely administered to adults to provide protection against bacteremia and at its peak in 2020 generated sales of over $1.1 billion. After the ACIP recommendation of PCV20 in late 2021 eliminated the need for PPSV23 in a large part of the covered population, PPSV23 has declined from more than 50% of the U.S. adult market share to less than 3%.

Polysaccharide vaccines induce a B-cell response only and do not induce a T-cell dependent immune response. In the absence of immunological memory responses, the resulting antibody responses are transient and cannot be boosted. Without the ability to provide long-lasting durable immunity, polysaccharide vaccines are not effective in children below two years of age. In addition, the antibody responses primarily consist of immunoglobulin M (“IgM”) antibodies that, due to their size, are restricted to blood and are unable to penetrate into lung tissue to protect against pneumonia. Therefore, polysaccharide vaccines such as PPSV23 are only thought to protect against blood-borne infections, such as bacteremia. Figure 1 below illustrates polysaccharide-induced T-cell independent antibody responses.

Figure 1.

Graphics adapted from Strugnell et al, Understanding Modern Vaccines, Vol 1, Issue 1, 61-88.

Polysaccharide vaccines also interfere with optimal use of PCVs, as they create a hyporesponsive immune effect. In particular, absent T-cell inducement, polysaccharide vaccines actually clear the memory B-cells that are formed following primary immunization with a PCV, thereby eliminating the ability to boost with subsequent vaccination. This historically has been a significant drawback of vaccination in older adults, which consisted of the administration of a limited spectrum PCV followed by the administration of a polysaccharide vaccine. Despite these shortcomings, PPSV23 historically has been widely used primarily to provide protection against circulating strains not contained in the currently available PCVs. The current routine standard-of-care in adults, which consists of the administration of either PCV20 or PCV21 alone or PCV15 followed by the administration of PPSV23, continues to include the alternative of a polysaccharide vaccine.

Pneumococcal Conjugate Vaccines

PCVs overcome the limitations of polysaccharide vaccines by conjugating the polysaccharide to a more immunogenic protein carrier containing T-cell epitopes. These T-cell epitopes provide CD4+ help, which is critical to the conversion of a traditional B-cell dependent immune response to a more robust combined B-cell and T-cell dependent immune response. The T-cell response causes immediate class switching of the B-cells from more rudimentary IgM antibodies prevalent with polysaccharide vaccines to more refined IgG antibodies. IgG antibodies are refined enough to penetrate into lung tissues to prevent pneumonia. Furthermore, as polysaccharide strands attach to multiple copies of the protein carrier, they create an inter-strand cross-linked matrix structure, which the immune system easily recognizes as foreign. The T-cell dependent immune response also generates memory B-cells that can be re-stimulated, creating a prime-boost immune response leading to a more robust and durable immune response and enabling the use of PCVs in young children. Figure 2 below illustrates this immune response:

Figure 2.

The first PCV, Prevnar, was a 7-valent vaccine that was launched in the United States in 2000. It included purified capsular polysaccharides of seven serotypes of Streptococcus pneumoniae (4, 6B, 9V, 14, 18C, 19F and 23F), each of which was individually conjugated to a T-cell-epitope-containing, nontoxic variant of diphtheria toxin known as CRM197 to produce

seven separate conjugates. To obtain approval, a large field efficacy study was conducted that demonstrated the vaccine’s efficacy in infants. Efficacy correlated with serological immune endpoints, as measured by IgG titers (a measurement of concentration), and a seroconversion threshold (or reference antibody concentration) of protection was defined. Prevnar is credited with tremendous medical and commercial success, having dramatically reduced circulating disease in children. However, after a number of years of widespread use, IPD incidence caused by strains not contained in the vaccine started to opportunistically rise, a phenomenon called serotype replacement, which led to the need for a broader-spectrum version of the vaccine.

In the race to develop a broader-spectrum PCV than Prevnar, two vaccines were successfully developed: Synflorix, a 10-valent PCV from GSK, and PCV13, a 13-valent PCV from Wyeth (subsequently acquired by Pfizer). Based on its broader coverage of then-emerging strains, PCV13 was adopted as the standard-of-care in the United States and Europe. Synflorix's use has been limited primarily to emerging countries.

PCV13 contains the seven serotypes originally included in Prevnar plus six more serotypes of Streptococcus pneumoniae (1, 3, 5, 6A, 7F and 19A) and was approved and launched in the United States in 2010. Each polysaccharide is conjugated to CRM197 to produce 13 individual conjugates, which are mixed into a final vaccine formulation and then adsorbed to alum. In 2010, PCV13 obtained FDA approval for the prevention of IPD in infants based on non-inferior IgG antibody responses relative to Prevnar, using the surrogate immune endpoints established by the prior Prevnar field efficacy study. While PCV13 failed to achieve non-inferiority on two of the common seven strains relative to Prevnar, it was granted approval across all 13 strains. Upon receipt of the ACIP recommendation, PCV13 replaced Prevnar in the infant market as the standard-of-care. This also created a “catch-up” population for those children previously vaccinated with Prevnar to provide protection against the incremental serotypes covered by PCV13.

In an effort to develop even broader-spectrum PCVs than PCV13, two vaccines were successfully developed for the adult and infant populations: PCV20, a 20-valent PCV from Pfizer, and PCV15, a 15-valent PCV from Merck.

PCV20 contains the 13 serotypes included in PCV13 plus seven more serotypes of Streptococcus pneumoniae (8, 10A, 11A, 12F, 15B, 22F and 33F) and was granted regulatory approval and launched in the United States in 2021 for the prevention of IPD and pneumonia in adults based on non-inferior OPA responses relative to PCV13 without the need for a field efficacy study. PCV20’s indication for the prevention of pneumonia caused by Streptococcus pneumoniae serotypes 8, 10A, 11A, 12F, 15B, 22F, and 33F in adults is approved under accelerated approval based on immune responses as measured by OPA assay. While PCV20 failed to achieve non-inferiority on serotype 8 relative to PPSV23, it was still granted approval across all 20 strains. In 2023, the FDA approved PCV20 for use in infants for the prevention of IPD, and for the prevention of otitis media caused by Streptococcus pneumoniae serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F without the need for a field efficacy study. While PCV20 failed to achieve non-inferiority for five of the 13 common (1, 3, 4, 9V and 23F) and one of the seven unique (12F) serotypes for the co-primary endpoint following the three-dose primary immunization series in the U.S. study, it was still granted FDA approval across all 20 strains for IPD.

PCV15 contains the 13 serotypes included in PCV13 plus two more serotypes of Streptococcus pneumoniae (22F and 33F) and was granted regulatory approval and launched in the United States in 2021 for the prevention of IPD in adults based on non-inferior OPA responses relative to PCV13 without the need for a field efficacy study. In 2022, the FDA approved PCV15 for use in infants for the prevention of IPD based on non-inferior IgG responses relative to PCV13 without the need for a field efficacy study.

In October 2021, the ACIP voted to recommend universal vaccination for the use of either PCV20 alone or PCV15 with PPSV23 for routine use in adults aged 65 years and older as well as for those between the ages of 19 and 64 years with certain underlying medical conditions or other risk factors who had not previously received a PCV or whose previous vaccination history was unknown. In June 2022, the ACIP voted to recommend that PCV15 may be used as an option to the then recommended PCV13 for children aged under 19 years according to then recommended PCV13 dosing and schedules. In October 2022, the ACIP voted to recommend a dose of PCV20 for adults aged 65 years and older at least five years after the last pneumococcal vaccine dose for those who haven't previously received PCV20. In June 2023, the ACIP voted to recommend the use of PCV20 as an option to PCV15 for routine use in children under the age of two, and as a “catch up” vaccination for healthy children between the ages of 24 and 59 months with incomplete PCV vaccination status and children between the ages of 24 and 71 months with certain underlying conditions and an incomplete PCV vaccination status. Further, the ACIP voted to recommend that children between the ages of two and 18 years with any risk condition who have received all recommended PCV doses before the age of six do not need additional doses if they have received at least one dose of PCV20. If children between the ages of two and 18 years with any risk condition received PCV13 or PCV15, but not PCV20, the ACIP recommended that they should receive a dose of PCV20 or PPSV23. The ACIP also voted to recommend that children between the ages of six and 18 years with any risk condition who have not received any dose of PCV13, PCV15 or PCV20 should receive a single dose of PCV15 or PCV20. When PCV15 is used in this instance, the ACIP recommended that it should be followed by a dose of PPSV23 at least eight weeks later if not previously given.

In June 2023, the ACIP also recommended shared clinical decision-making regarding PCV20 use for adults aged 65 years and older who have completed the recommended vaccine series with both PCV13 and PPSV23.

As a further example of the need for broader-protection vaccines to prevent IPD highlighted by the public health community, another vaccine was successfully developed for the adult population: PCV21, a 21-valent PCV from Merck. Unlike predecessor PCVs, PCV21 does not contain each of the historically circulating serotypes covered in previously approved PCVs. PCV21 contains 11 of the 20 serotypes included in PCV20 (serotypes 3, 6A, 7F, 8, 10A, 11A, 12F, 15B, 19A, 22F and 33F) plus 10 more serotypes of Streptococcus pneumoniae (serotypes 9N, 15A, 16F, 17F, 20, 23A, 23B, 24F, 31 and 35B). PCV21 was granted regulatory approval and launched in the United States in 2024 for the prevention of IPD and pneumonia (serotypes 3, 6A, 7F, 8, 9N, 10A, 11A, 12F, 15A, 15C, 16F, 17F, 19A, 20A, 22F, 23A, 23B, 24F, 31, 33F, and 35B) in adults based on non-inferior OPA responses relative to PCV20 without the need for a field efficacy study. PCV21’s indication for the prevention of pneumonia is approved under accelerated approval based on immune responses as measured by OPA.

In June 2024, the ACIP voted to recommend PCV21 as an option to either PCV20, or PCV15 with PPSV23, for (i) adults aged 65 years and older who have not previously received a PCV or whose previous vaccination history is unknown, (ii) adults between the ages of 19 and 64 with certain underlying medical conditions or other risk factors who have not previously received a PCV or whose previous vaccination history is unknown and (iii) adults aged 19 years and older who have received PCV13 but not all recommended doses of PPSV23. Additionally, the ACIP recommended shared clinical decision-making regarding a supplemental dose of PCV21 for adults aged 65 and older who have completed their vaccine series with both PCV13 and PPSV23.

In October 2024, the ACIP expanded its recommendation by lowering the age-based pneumococcal vaccination guidelines for pneumococcal vaccination in adults from 65 years and older to 50 years and older. In line with this recommendation, the ACIP recommends either a dose of PCV20 or PCV21, or PCV15 with PPSV23, for (i) adults aged 50 and older who have not previously received a PCV or whose previous vaccination history is unknown and (ii) adults between the ages of 19 and 49 with certain underlying medical conditions or other risk factors who have not previously received a PCV or whose previous vaccination history is unknown.

Drawbacks of Current PCVs

Routine immunization with PCVs has been effective in dramatically lowering the incidence of IPD in both adults and children in the United States and other industrialized nations. However, due to a phenomenon called serotype replacement, strains that are not covered by existing vaccines are increasing in prevalence. As published in 2022, 35% and 37% of IPD incidence in 2018 for children under the age of five and adults aged 65 years and older, respectively, were caused by strains beyond the 20 strains covered by PCV20. Efforts to improve upon standard-of-care vaccines center around expanding the valency of PCVs to address the strains driving residual pneumococcal disease. However, limitations due to conventional conjugation chemistry and carrier suppression have complicated those efforts, and notwithstanding the recent approvals of PCV21 in adults, PCV20 and PCV15, there remains a significant need for broader-spectrum PCVs that address both currently circulating and historically prevalent serotypes, as evidenced by the fact that despite the coverage of PCV21 and PCV20, the combination of PCV15 and PPSV23 remains universally recommended when adults turn 50 in the United States, as an alternative to either PCV21 or PCV20 alone, given the broader-spectrum coverage of these two vaccines combined compared to PCV21 or PCV20. Although PCV21 covers more incidence of disease, it does not address several of the serotypes historically covered, many of which continue to circulate today.

While vaccination with current PCVs has been effective in dramatically lowering the incidence of IPD in both adults and children in the United States and other industrialized nations, current PCVs suffer from the following drawbacks.

Serotype Replacement

Since the introduction of PCV13, there has been a decrease in incidence of disease attributable to the serotypes included in the vaccine. However there has been a phenomenon called serotype replacement, whereby a void is created when serotypes are taken out of circulation after widespread vaccination. As a result, serotypes not covered by PCV13 now cause residual pneumococcal disease. Broader-spectrum PCVs were historically required to maintain protection against historically pathogenic strains while expanding coverage to address current circulating and emerging strains. This serotype replacement has led to the development of a third generation of conventional PCVs, inclusive of PCV15 and PCV20. Although PCV21 was approved despite lacking protection against certain historically pathogenic strains, it is only approved in the adult population and did not receive a preferred recommendation despite its disease coverage, and is recommended solely as an alternative to PCV20 alone or PCV15 and PPSV23. VAX-31, if approved, would increase coverage to more than 95% of IPD currently circulating in the U.S. adult population aged 50 and over. In the pediatric population, VAX-31 is designed to cover approximately 92% of IPD in U.S. children under five years of age and approximately 96% of otitis media due to Streptococcus pneumoniae in U.S. children five years of age or under.

Pneumococcal disease surveillance has been conducted by the CDC in the United States and by the UK Health Security Agency. As shown in Figure 3, IPD cases in adults in the United States initially declined after the introduction of PCV13 but have since plateaued. The rate of serotype replacement has been more pronounced in the United Kingdom. Figure 4 shows the approximate IPD incidence rates in the United Kingdom caused by the incremental strains over and above those in PCV13, which increased over the last three years of surveillance.

Figure 3.Figure 4.

(1) U.S. CDC Active Bacterial Core Surveillance Annual Reports

(2) Ladhani et al, Lancet Infectious Disease, 2018 Apr.; 18(4):441-45 inclusive of unpublished raw data

While some of these strains are covered by PPSV23, that vaccine only protects against blood-borne infections and not pneumonia, leaving patients vulnerable to infection. Although PCV21, PCV20 and PCV15 address more disease-causing strains than PCV13, we believe there remains a significant need for even broader-spectrum vaccines to address a greater number of currently circulating and emerging strains.

Carrier Suppression

Technical constraints inherent to conventional conjugation chemistry limit the coverage of current PCVs due to a phenomenon known as carrier suppression. In particular, traditional conjugation methods cannot control where conjugation of the polysaccharide occurs on the protein carrier. The protein carrier used in all versions of Prevnar is CRM197, a diphtheria toxin with a single point mutation rendering it non-toxic. The CRM197 protein contains 39 lysines, approximately 20% of which border relevant T-cell epitopes. Conventional conjugation chemistry randomly attaches the polysaccharide to any of the numerous lysines located on the protein carrier. When a polysaccharide is covalently bound to a protein carrier at a lysine residue that is co-resident with a T-cell epitope, it blocks the presentation of the T-cell epitope to the immune system, thus preventing the induction of a T-cell response. The masking of these critical epitopes prevents the conversion to a T-cell dependent immune response and negates the benefit of the protein carrier.

Meanwhile, the B-cell epitopes of both the protein carrier and the antigen are presented to the immune system, causing B-cells to the respective immunogens to compete with one another for the T-cell help engendered by unblocked T-cell epitopes. This competition for T-cell helps diminish the immune response to the polysaccharide antigen of interest, resulting in carrier suppression.

The result of carrier suppression is a decrease in the targeted immune response to the disease-specific polysaccharides, which intensifies with higher cumulative amounts of protein carrier. This phenomenon impedes the ability to expand coverage of current PCVs and has been shown consistently when broader-spectrum versions of conventional PCVs have been compared to lesser-valent versions. When PCV20 was compared to PCV13 in a well-controlled Phase 3 study in infants, the IgG antibody responses directed against the polysaccharides of interest for all thirteen of the common strains in each vaccine were lower for PCV20 (Figure 5). In 2020, Pfizer presented results of a well-controlled Phase 3 study in adults, aged 60 and over, where they compared PCV20 to PCV13. In that study, the OPA responses directed against the polysaccharides of interest for all thirteen of the common strains were lower for PCV20 (Figure 6).

Figure 5.Figure 6.

1 IgG Geometric Mean Concentrations post-dose 4 – Prevnar 20 Biologics License Application ("BLA") Clinical Review Memorandum by FDA (STN: 125731/189). April 27, 2023.

2 PCV20 BLA Clinical Review Memorandum. STN: 125731/0 June 8, 2021.

Conventional Chemistry

The problem of carrier suppression is compounded by conventional conjugation chemistry used to make current PCVs, including PCV15, PCV20 and PCV21, which requires a higher amount of CRM197 protein carrier than polysaccharide antigen to complete the conjugation reaction, as well as long reaction times and harsh conditions that can damage the critical epitopes on the polysaccharide antigens. This results in a higher ratio of protein carrier to polysaccharide antigen in their monovalent conjugates (approximately 1.1 on average), as well as a much higher amount of cumulative protein carrier in the final formulation compared to the amount of any given polysaccharide antigen. For example, in the marketed PCV20 formulation, there are 51 micrograms of the protein carrier, CRM197, relative to 2.2 micrograms of each polysaccharide (except serotype 6B at 4.4 micrograms), and in the marketed PCV21 formulation, there are 65 micrograms of CRM197, relative to 4.0 micrograms of each polysaccharide. With substantially more protein carrier in the vaccines than polysaccharide antigen, the carrier suppression effect discussed above is exacerbated.

Our Solution

We are leveraging our cell-free protein synthesis platform to develop potentially superior conjugate vaccines for adult and pediatric indications. Our solution to the drawbacks with conventional conjugate vaccine techniques represents the first of three main applications of our platform.

Platform Application One: Creating Superior Conjugate Vaccines

Using our cell-free protein synthesis platform, we are developing superior, novel carrier-sparing PCVs designed to have broader-spectrum coverage in an effort to address historic, current and future residual disease in ways that conventional technologies cannot. We are able to design our investigational PCVs using site-specific conjugation in an effort to ensure optimal exposure of targeted immunogenic T-cell epitopes on protein carriers. This enables us to create broader-spectrum conjugate vaccine candidates using carrier-sparing conjugates designed to minimize carrier suppression while maintaining protective immunogenicity.

Synthesizing proteins outside of a living host cell provides us greater freedom to design and produce specific proteins of interest under optimized conditions. We separate the precise cellular machinery required for transcription, translation and energy production—the critical components for protein production—into an Escherichia coli ("E. coli")-derived extract. We can then optimally express a single protein carrier by adding the plasmid-DNA encoding that protein into the extract mixture.

Site-Specific Conjugation

Within a protein carrier, we can substitute non-native amino acids (“nnAAs”) for native amino acids at specific sites. These inserted nnAAs serve as conjugation anchors that permit the attachment of antigens, including polysaccharides, at a specific site on a protein carrier to ensure optimal exposure of B-cell and/or T-cell epitopes to induce the desired immune response. This precise site-specific linkage is not possible using conventional conjugation chemistry with conventional carrier proteins and affords an advantage to our conjugate vaccine candidates. Figure 7 below depicts our method of inserting nnAAs into a protein carrier, where the DNA sequence has been modified to permit nnAA incorporation into the protein at pre-selected sites using a nnAA-RNA permitting transcription and translation of the protein in the ribosome to yield the protein carrier with nnAAs site-specifically incorporated, facilitating site-specific conjugation.

Figure 7.

Most conjugate vaccines available today use a non-disease-specific protein carrier, CRM197, in order to leverage T-cell epitopes to induce a T-cell dependent immune response. This traditional method produces a heterogeneous mixture of conjugates with blocked and unblocked T-cell epitopes in a large immunogenic cross-linked matrix structure. In contrast, the precision and flexibility of cell-free protein expression, together with our ability to insert nnAAs, allow us to construct our proprietary enhanced protein carrier (“eCRM”) with pre-determined conjugation sites. Our method produces more homogenous conjugates that provide for the consistent exposure of T-cell epitopes and likewise form a large, immunogenic cross-linked matrix structure. By precisely conjugating polysaccharides to eCRM in a way that provides for optimal exposure of T-cell epitopes to the immune system, we can heighten immunogenicity attainable with conjugate vaccines.

The figures below illustrate the site-specific conjugation process. Figure 8 shows site-specific conjugation of the polysaccharide to the protein carrier, avoiding the T-cell epitopes. Figure 9 shows the inter-strand cross-linked matrix, which is the structure of each monovalent conjugate included in the final vaccine.

Figure 8.Figure 9.

We believe consistent exposure of T-cell epitopes should translate to higher potency of the protein carrier on a weight-to-weight basis. To harness this potential potency advantage, we have elected to construct conjugates with a lower ratio of protein carrier to polysaccharide than conventional PCVs. Our clinical studies to date validated our carrier-sparing approach to develop broader-spectrum PCVs. As a result, we believe we can incorporate more monovalent conjugates to

create an even more broad-spectrum vaccine with less protein carrier per conjugate in order to minimize carrier suppression.

Better Chemistry

We also employ a rapid and less harsh chemistry method called copper-free click chemistry to site-specifically conjugate the polysaccharides to eCRM. We believe this distinctive technique is a better controlled, more efficient and faster method of conjugation relative to conventional chemistry used to make traditional PCVs. The click chemistry conjugation reaction is designed to cause less damage to the critical immunogenic epitopes on the protein carrier or the target antigen.

Our PCV Franchise

We are developing broad-spectrum investigational PCVs designed to improve serotype coverage compared to current standard-of-care PCVs and minimize carrier suppression. We currently have three PCV candidates in our differentiated PCV franchise: VAX-31, a 31-valent, broad-spectrum, carrier-sparing investigational PCV, which we are developing for both the infant and adult populations, VAX-24, a 24-valent, broad-spectrum, carrier-sparing investigational PCV for which we have completed a Phase 2 trial in both the adult and infant populations, and VAX-XL, a third-generation PCV candidate designed to provide the broadest coverage of any PCV currently in development. VAX-31, the broadest-spectrum PCV in the clinic, is designed to provide protection against both currently circulating and historically prevalent serotypes and cover approximately 95% and 92% of IPD circulating in the U.S. adult (ages 50 and older) and infant (under the age of five) populations, respectively. The 31 serotypes included in VAX-31 are associated with high case-fatality rates, antibiotic resistance and meningitis. VAX-24 covers more serotypes than any pneumococcal infant vaccine on the market today.

As shown in Figure 10 below, there are critical differences between VAX-31 and VAX-24 and other currently available PCVs relating to the protein carrier, particularly the use of site-specific conjugation and the milder reaction conditions. We achieve site-specific conjugation through the insertion of multiple nnAAs, which is not possible with the conventional chemistry used for making other PCVs. The click chemistry we use for site-specific conjugation may also minimize damage to the critical immunogenic epitopes on the protein carrier and the polysaccharides through milder and shorter reactions, while other PCVs use conventional chemistries that involve harsher and longer reaction conditions.

Figure 10.

Furthermore, VAX-31 and VAX-24 improve upon the serotype spectrum of coverage relative to PCV15 and PCV20 in both the adult and infant populations, and VAX-31 improves on the same in the adult population relative to PVC21, and use less protein carrier per conjugate than these conventional chemistry PCVs. In aggregate, VAX-31 contains more protein carrier, and VAX-24 contains a similar amount of protein carrier, relative to PCV15 and PCV20. We believe the resulting decreased carrier burden per conjugate of VAX-31 and VAX-24 are critical for minimizing carrier suppression and producing broader-spectrum pneumococcal vaccines without sacrificing immunogenicity.

Where appropriate, we capitalize on the efficiencies of well-established clinical, manufacturing and regulatory precedents by leveraging conventional methods for the development of our PCV candidates. For example, our polysaccharide antigens are primarily made using conventional fermentation and purification techniques and activated through conventional methods. They are also labeled through conventional amination methods prior to being conjugated to eCRM. In addition, we use the same critical quality attribute assays for molecular weight and free polysaccharide that have served as the

physicochemical measures of conjugates and also serve as predictors of their immunogenicity in vivo. We also use conventional IgG and OPA serological assays to gauge the immunogenicity of our conjugates, which have served as surrogate immunological endpoints in clinical studies that enabled the approval of PCV13, PCV15, PCV20 and PCV21.

We are pursuing a well-characterized clinical development path for our PCV candidates, consistent with other PCV developers. We have been able to conduct smaller and shorter clinical trials that target immune endpoints (e.g., OPA and IgG responses) previously recognized by regulatory authorities, and anticipate that we will be able to conduct such studies going forward. Pfizer applied this approach to the development of PCV13 and PCV20 and Merck applied it to the development of PCV15 and PCV21. Based on this standard, as a prerequisite for regulatory approval, we believe that any investigational PCV will have to be compared to the standard-of-care at the time a clinical trial is initiated. Currently, the standard-of-care for routine use is either PCV20 or PCV21 alone or PCV15 followed by PPSV23 in adults and PCV20 or PCV15 in infants.

Clinical Development Overview

We are pursuing clinical development for adults with VAX-31 and, for the pediatric population, have completed a Phase 2 study with VAX-24 and are currently conducting a Phase 2 study with VAX-31.

Adult Indication

We have selected VAX-31 to advance to an adult Phase 3 program, which was initiated in December 2025.

For VAX-31, we achieved clinical proof of concept in September 2024 when we announced positive topline results from a Phase 1/2 study evaluating the safety, tolerability and immunogenicity of VAX-31 in healthy adults aged 50 and older. Based on these positive results, we selected the High Dose of VAX-31 to advance to an adult Phase 3 program. Following an FDA End-of-Phase 2 meeting, we initiated a Phase 3 pivotal, non-inferiority study in December 2025 and expect to announce topline safety, tolerability and immunogenicity data in the fourth quarter of 2026. In January 2026, we announced the initiation of an additional Phase 3 trial evaluating VAX-31 when administered concomitantly with a licensed, high-dose seasonal influenza vaccine in pneumococcal-naïve adults aged 50 years and older (“OPUS-2”). In February 2026, we announced the initiation of a separate Phase 3 study evaluating VAX-31 in adults previously vaccinated with lower-valency pneumococcal vaccines (“OPUS-3”). We expect to report safety, tolerability and immunogenicity data from the OPUS-2 and OPUS-3 studies in the first half of 2027. We are also planning for a manufacturing consistency study (e.g. a lot-to-lot study). Subject to the results of the adult Phase 3 studies, we would expect to submit a BLA shortly following the completion of the last Phase 3 study.

For adults, the FDA has granted VAX-31 BTD for the prevention of IPD as well as pneumonia caused by Streptococcus pneumoniae. A BTD is designed to expedite the development and review of drugs that are intended to treat serious or life-threatening conditions and is based upon preliminary clinical evidence indicating that the drug or vaccine may demonstrate substantial improvement over available therapies on one or more clinically significant endpoints.

Infant Indication

We have completed a Phase 2 study with VAX-24 and and are currently conducting a Phase 2 study with VAX-31 for the prevention of IPD in infants.

In March 2025, we announced positive topline, interim data from the VAX-24 infant Phase 2 study, a randomized, observer-blind, dose-finding two-stage clinical study evaluating the safety, tolerability and immunogenicity of VAX-24 in healthy infants that enrolled 803 participants.

In November 2025, we announced final safety, tolerability, and immunogenicity results from the VAX-24 infant Phase 2 study that were consistent with the positive interim data reported in March 2025 and showed that VAX-24 elicited robust, dose-dependent immune responses, with little to no evidence of carrier suppression observed.

In this study, VAX-24 was well-tolerated and demonstrated a safety profile similar to PCV20 across all doses studied. The results from this study informed advancement of our modified VAX-31 infant Phase 2 dose-finding study. The final positive data from the VAX-24 infant Phase 2 dose-finding study further validated our rationale for exploring higher doses in the ongoing VAX-31 infant Phase 2 study.

For VAX-31, in December 2024 we announced that the first participants were dosed in the first stage of a Phase 2 randomized, dose-finding study of VAX-31 in healthy infants, and in February 2025, we announced that the ongoing study

had advanced to the second stage of the study and that the first participants had been dosed. In September 2025, we announced advancement of the modified VAX-31 infant Phase 2 randomized, dose-finding study to the third and final stage. The study advanced to the third and final stage following modifications to the protocol to add a new dose arm to evaluate the VAX-31 Optimized Dose (majority of serotypes dosed at 4.4mcg and the balance dosed at 3.3mcg) and discontinue enrollment in the Low Dose arm. The Middle and High Dose arms are continuing as planned. In January 2026, we announced that we had completed enrollment of this study.

Clinical Data: Adult Indication

We are using OPA titers as the primary immunogenicity endpoint for the VAX-31 program in adults. OPA is believed to be the primary protective mechanism against pneumococcal disease. In addition, we are measuring IgG responses as a secondary endpoint, as such responses may serve as supportive evidence of immunogenicity for comparison. We believe that these endpoints, if met in a Phase 3 trial, will be sufficient to obtain regulatory approval of VAX-31 and that we will not need a clinical field efficacy study.

The FDA has previously approved pneumococcal vaccines upon the establishment of non-inferiority based on a head-to-head comparison using established surrogate immune endpoints in the target population. For adults, PCV13 was approved based on the establishment of non-inferiority of OPA responses relative to PPSV23, on a strain-by-strain basis, where non-inferiority was defined as greater than or equal to 0.50 of the lower limit of the two-sided 95% confidence interval of the OPA geometric mean titer ratio. PCV20 was approved based on the same non-inferiority criterion but compared with PCV13 and PPSV23, while PCV15 was approved based on the same non-inferiority for the common serotypes, but a different non-inferiority criterion for the incremental strains compared to PCV13. PCV21 was approved based on the same non-inferiority criterion as PCV15, but compared to PCV20.

The VAX-31 Phase 1/2 clinical study was a randomized, observer-blind, active-controlled, dose-finding clinical study designed to evaluate the safety, tolerability and immunogenicity of VAX-31 at three dose levels (Low, Middle and High) and compared to PCV20 in 1,015 healthy adults aged 50 and older. In the Low, Middle and High Doses, all serotypes were dosed at 1.1mcg, 2.2mcg and 3.3mcg, respectively, except serotypes 1, 5 and 22F, which were dosed at 1.65mcg, 3.3mcg, and 4.4mcg, respectively. The Phase 1 portion of the study evaluated the safety and tolerability of a single injection of VAX-31 at three dose levels and compared to PCV20 in 64 healthy adults 50 to 64 years of age. In January 2024, we announced that the first participants were dosed in the Phase 2 portion of the Phase 1/2 study of VAX-31 in healthy adults. The initiation of the Phase 2 portion occurred after an independent Data Monitoring Committee conducted an assessment of the Phase 1 safety and tolerability results and recommended that the study proceed as planned to Phase 2. Phase 1 participants were evaluated for immunogenicity, and the Phase 1 safety, tolerability and immunogenicity data was pooled with the participants in the Phase 2 portion of the study. The Phase 2 portion of the study evaluated the safety, tolerability and immunogenicity of a single injection of VAX-31 at the same three dose levels and compared to PCV20, in 951 healthy adults 50 years of age and older. Participants were randomized equally in four separate arms and, 30 days after dosing, serology samples were collected to assess immunogenicity. The immunogenicity objectives of the study included an assessment of the induction of antibody responses, using OPA and IgG at each of the three VAX-31 doses and compared to PCV20, for the 20 serotypes in common, as well as for the additional 11 serotypes contained in VAX-31, but not in PCV20. Participants in the study were evaluated for safety through six months after vaccination. The study was conducted at approximately 25 sites in the United States. In January 2024, we announced the completion of enrollment in the Phase 1/2 clinical study evaluating VAX-31 in healthy adults aged 50 and older.

Figure 12 is a schematic of the overall study design of our VAX-31 adult Phase 1/2 study:

Figure 12.

In September 2024, we announced positive topline results from the study.

Safety and Tolerability Findings:

As shown in Figure 13, based on the full six-month safety data, VAX-31 was observed to be well tolerated and demonstrated a safety profile at all doses studied through the full six-month evaluation period similar to PCV20. As shown in Figure 14 and Figure 15, frequently reported local and systemic reactions were generally mild-to-moderate, resolving within several days of vaccination, with no meaningful differences observed across the cohorts. No serious adverse events were considered to be related to study vaccines.

Figure 13.

Figure 14.

Figure 15.

Immunogenicity Findings:

As shown in Figures 16 and 17, VAX-31 showed robust OPA immune responses for all 31 serotypes at all doses studied. At the Middle and High Doses, VAX-31 met or exceeded the regulatory immunogenicity criteria for all 31 serotypes and, at the Low Dose, for 29 of 31 serotypes.

As shown in Figure 16, at the Middle and High doses, VAX-31 met or exceeded the OPA response non-inferiority criteria (lower bound of the 2-sided 95% confidence interval of the OPA GMR is greater than 0.5) for all 20 serotypes common with PCV20. At the VAX-31 High Dose, average OPA immune responses were greater for 18 of 20 serotypes compared to PCV20 (GMR greater than 1.0), with seven of these serotypes achieving statistically higher immune responses compared to PCV20 (lower bound of the 2-sided 95% confidence interval of the OPA GMR is greater than 1.0). At the Middle Dose, 13 of 20 serotypes had a GMR greater than 1.0 and five serotypes achieved statistically higher immune responses compared to PCV20. At the Low Dose, 18 of 20 serotypes met the OPA response non-inferiority criteria, 8 of 20 serotypes had a GMR greater than 1.0 and three serotypes achieved statistically higher immune responses.

Figure 16.

As shown in Figure 17, for all 11 incremental serotypes unique to VAX-31, and not in PCV20, all three doses met the superiority criteria (lower bound of the 2-sided 95% confidence interval of the difference in the proportions of participants with a ≥4-fold increase from day 1 to month 1 is greater than 10%, and lower bound of the 2-sided 95% confidence interval of the OPA GMR is greater than 2.0).

Figure 17.

Based on these positive results, we selected the High Dose of VAX-31 to advance to an adult Phase 3 program. Following an FDA End-of-Phase 2 meeting, we are advancing a comprehensive Phase 3 adult clinical program for VAX-31 to support a planned BLA submission. The announced Phase 3 clinical studies, which were finalized in consultation and alignment with the FDA, include the pivotal, noninferiority trial evaluating VAX-31 for the prevention of IPD and pneumonia in adults (OPUS-1); a trial evaluating VAX-31 when administered concomitantly with a licensed, high-dose seasonal influenza vaccine in pneumococcal-naïve adults (OPUS-2); and a trial in adults who have previously received a pneumococcal vaccine (OPUS-3), all of which are currently enrolling participants. Across these three studies, approximately 6,000 adults are expected to be enrolled in total, of whom approximately 3,400 will receive VAX-31, with the intent to generate a broad and robust safety, tolerability and immunogenicity dataset. We are also planning for a manufacturing consistency study (e.g., a lot-to-lot study).

OPUS-1 is evaluating the safety, tolerability and immune responses of VAX-31 in approximately 3,560 adults aged 50 and older through direct, head-to-head comparisons with both PCV21 and PCV20, the current standard-of-care PCVs, with the objective of establishing a best-in-class profile for VAX-31. The trial is also evaluating the safety, tolerability and immune responses of VAX-31 in approximately 440 adults aged 18-49. OPUS-1 is being conducted at approximately 50 sites in the United States.

The key primary immunogenicity objectives of this trial are to demonstrate (i) noninferiority if the lower bound of the two-sided 95% confidence interval for the OPA GMR of VAX-31 exceeds 0.667 compared with PCV21 and/or PCV20 for the 28 serotypes shared with one or both comparators and (ii) superiority if the lower bound of the two-sided 95% confidence interval of the OPA GMR exceeds 2.0 for the three serotypes unique to VAX-31 and serotype 20B versus the comparator vaccines. The trial is also evaluating the safety, tolerability and immune responses of VAX-31 in adults aged 18-49. Key secondary immunogenicity objectives are included to evaluate VAX-31 based on additional measures of non-inferiority, superiority and statistically greater immune responses.

OPUS-2 is a randomized, double-blind, placebo-controlled clinical trial designed to evaluate the safety, tolerability and immunogenicity of VAX-31 when administered either concomitantly with or one month following administration of a licensed, high-dose seasonal influenza vaccine in pneumococcal-naïve, healthy U.S. adults aged 50 years and older. The study is expected to enroll approximately 1,300 participants at approximately 25 sites in the United States. The results of this descriptive study are intended to inform the design of a potential post-licensure outcomes study that further evaluates VAX-31 in concomitant use with an influenza vaccine and to provide supportive evidence as part of the broader Phase 3 dataset.

OPUS-3 is a randomized, double-blind, active-controlled, descriptive clinical trial designed to evaluate the safety, tolerability and immunogenicity of a single dose of VAX-31 in approximately 720 healthy U.S. adults aged 50 years and

older with a history of prior pneumococcal vaccination at least six months prior. The study will be conducted at approximately 30 sites in the United States.

Contextual Information: VAX-24 Adult Indication

Phase 1/2 Clinical Proof-of-Concept Study in Adults Aged 18 to 64

Our first-in-human study was a randomized, double-blind, dose-finding, controlled Phase 1/2 clinical proof-of-concept study designed to evaluate the safety, tolerability and immunogenicity of VAX-24 in healthy adults aged 18 to 64. The Phase 1 portion of the study evaluated the safety and tolerability of a single injection of VAX-24 at three dose levels, 1.1mcg, 2.2mcg and 2.2mcg/4.4mcg, and compared to PCV20 in 64 healthy adults aged 18 to 49. Participants were randomized equally in four separate arms and were evaluated for safety 8 and 29 days after dosing. The Phase 2 portion evaluated the safety, tolerability and immunogenicity of a single injection of VAX-24 at the same three dose levels and compared to a single injection of PCV20 in 771 healthy adults 50 to 64 years of age. Participants were randomized equally in four separate arms and approximately 28 days after participants were dosed, samples were collected to assess immunogenicity. The immunogenicity objectives of the Phase 2 portion of the study included an assessment of the induction of antibody responses, using OPA and IgG, at each of the three VAX-24 doses and compared to PCV20, and for the additional four serotypes contained in VAX-24 (and PPSV23), but not in PCV20, the percentage of subjects that experienced a four-fold rise in antibody titers. Participants in the study were evaluated for safety through six months after vaccination.

Figure 18 is a schematic of the overall study design of our Phase 1/2 study:

Figure 18.

In October 2022, we announced positive topline results from both the Phase 1 and Phase 2 portions of the study.

VAX-24 met the primary safety and tolerability objectives, demonstrating a safety profile similar to PCV20 for all doses studied. Frequently reported local and systemic reactions were generally mild-to-moderate, resolving within several days of vaccination, with no difference observed across the cohorts. No serious adverse events or new onset chronic illnesses were considered to be related to study vaccines.

Figure 19.

Local Solicited AEs Similar to PCV20 and Across Cohorts Through Day 7Systemic Solicited AEs Similar to PCV20 and Across Cohorts Through Day 7

In this study, VAX-24 demonstrated robust OPA and IgG immune responses for all 24 serotypes at all doses studied (1.1mcg, 2.2mcg, 2.2mcg/4.4mcg). At the conventional 2.2mcg dose, which we plan to advance to a potential Phase 3 program, VAX-24 met or exceeded the established regulatory immunogenicity standards for all 24 serotypes. At this dose, VAX-24 met the standard OPA response non-inferiority criteria for all 20 serotypes common with PCV20, of which 16 serotypes (3, 4, 6B, 7F, 8, 9V, 10A, 11A, 12F, 14, 15B, 18C, 19A, 19F, 23F and 33F) achieved higher immune responses and four serotypes (9V, 18C, 19F and 33F) reached statistical significance. Additionally, at all three doses, VAX-24 met the standard superiority criteria for all four serotypes (2, 9N, 17F and 20B) unique to VAX-24.

Figure 20.

Figure 21.

Regulatory Threshold for Superiority (LL95%CI > 10%)

Based on the results of this study, the FDA granted a BTD for VAX-24 for the prevention of IPD in adults.

Phase 2 Clinical Study in Adults 65 and Older

To add to the body of data in adults, we conducted a separate Phase 2 study in adults aged 65 and older. This study was a randomized, double-blind, dose-finding, controlled Phase 2 study designed to evaluate the safety, tolerability and immunogenicity of a single injection of VAX-24 at the same three dose levels evaluated in the Phase 1/2 study, 1.1mcg, 2.2mcg and 2.2mcg/4.4mcg, and compared to a single injection of PCV20 in 207 healthy adults aged 65 and older. Participants were randomized equally in four separate arms and approximately 28 days after participants were dosed, samples were collected to assess immunogenicity. The immunogenicity objectives of the study include an assessment of the induction of antibody responses, using OPA and IgG, at each of the three VAX-24 doses and compared to PCV20, and for the additional four serotypes contained in VAX-24 (and PPSV23), but not in PCV20, the percentage of subjects that experience a four-fold rise in antibody titers. This study was designed to inform the powering of a Phase 3 study and was not powered to demonstrate non-inferiority. Participants in the study also were evaluated for safety through six months after vaccination.

Figure 22 is a schematic of the overall study design of our Phase 2 study in adults aged 65 and older:

Figure 22.

On April 17, 2023, we announced positive results from this Phase 2 study of VAX-24 in adults aged 65 and older, as well as data from the full six-month safety assessment and prespecified pooled immunogenicity analyses from both the Phase 2 study in adults aged 65 and older and the prior Phase 1/2 study in adults aged 18-64.

In this Phase 2 study, VAX-24 demonstrated robust OPA immune responses across all 24 serotypes at all doses studied (1.1mcg, 2.2mcg, and 2.2mcg/4.4mcg), confirming the prior Phase 2 adult study results. The VAX-24 2.2mcg dose, which we had planned to advance to a potential Phase 3 program prior to our decision to advance exclusively VAX-31, showed an overall improvement in immune responses compared to PCV20 relative to the results from the prior Phase 2 study in adults

aged 50-64. The six-month safety data from both adult studies showed safety and tolerability results for VAX-24 similar to PCV20 at all doses studied.

Figure 23.

Local Solicited AEs Similar to PCV20 and Across Cohorts Through Day 7Systemic Solicited AEs Similar to PCV20 and Across Cohorts Through Day 7

Consistent with prior Phase 2 study, the 2.2mcg dose demonstrated higher OPA GMR for 16 out of the 20 shared serotypes. The 2.2mcg dose showed robust immune responses for all 24 serotypes.

Figure 24.

Figure 25.

Threshold for Superiority (LL95%CI > 10%)

Prespecified Pooled Immunogenicity Analyses of Data from VAX-24 Adult Phase 2 Studies

Additionally, we conducted prespecified pooled analyses of data from both adult Phase 2 studies to evaluate the immunogenicity of VAX-24 in participants aged 50 and older and aged 60 and older, which are representative populations for the potential VAX-24 Phase 3 pivotal study. The prespecified pooled immunogenicity analyses of data from both adult Phase 2 studies showed the VAX-24 2.2mcg dose met the OPA non-inferiority criteria for all 20 serotypes common with PCV20 and met the superiority criteria for the four additional serotypes unique to VAX-24. In the pooled group with participants aged 50 and older, VAX-24 met the OPA response non-inferiority criteria for all 20 serotypes common with PCV20, of which 16 achieved higher immune responses and four reached statistical significance. In the pooled group with participants aged 60 and older, VAX-24 met the OPA response non-inferiority criteria for all 20 serotypes common with PCV20, of which 17 achieved higher immune responses and three reached statistical significance.

Figure 26.

Combined Six-Month Safety Data from Both Adult VAX-24 Studies

In April 2023, we also reported the full six-month safety results from the VAX-24 Phase 2 study in adults aged 65 and older and the VAX-24 Phase 1/2 study in adults aged 18-64. Through six months, VAX-24 demonstrated safety and tolerability results similar to PCV20 across all ages and doses studied. Frequently reported local and systemic reactions were generally mild-to-moderate, resolving within several days of vaccination, with no meaningful difference observed across the cohorts. Further, no serious adverse events or new onset chronic illnesses were considered to be related to study vaccines. In a VAX-24 arm of the Phase 2 study in adults aged 65 and older, one participant with multiple pre-existing risk factors suffered a sudden cardiac death six months post-vaccination, which the Principal Investigator determined was not related to study vaccine due to the participant’s history of hypertensive cardiovascular disease.

Figure 27.

VAX-24 — Low Dose

(1.1mcg)VAX-24-Middle

Dose (2.2mcg)VAX-24 - Mixed Dose

(2.2mcg/4.4mcg)PCV20

Number of Subjects with261258260262

Unsolicited TEAE, n (%)38 (14.6)28 (10.9)30 (11.5)42 (16.0)

Related Unsolicited TEAE, n (%)5 (1.9)13 (5.0)7 (2.7)13 (5.0)

MAAE, n (%)32 (12.2)29 (11.2)27 (10.4)37(14.1)

Related MAAE, n (%)001 (0.4)0

NOCI, n (%)4 (1.5)4 (1.6)7 (2.7)5 (1.9)

Related NOCI, n (%)0000

SAE, n (%)3 (1.1)4 (1.6)2 (0.77)4 (1.5)

Related SAE, n (%)0000

Death, n (%)0
1 (0.39)1
00

Related Death, n (%)0000

(1) 66-year-old white, obese male (BMl: 47.4) with hypertension. No solicited AEs were reported after vaccination. Participant suffered sudden cardiac death six months post-vaccination determined by Principal Investigator to be not related to study product due to participant's history of hypertensive cardiovascular disease.

TEAE = Treatment emergent adverse events

Excludes Solicited AEs

Clinical Programs: Infant Indication

We expect the clinical development of VAX-24 and VAX-31 in infants to follow similar approaches utilized for PCV13, PCV15 and PCV20, where vaccine effectiveness against IPD was inferred from immunologic correlates, and approvals are based on non-inferiority comparisons of IgG responses and totality of data, whereas in the adult population approvals have been based on non-inferiority comparisons of OPA responses. Consistent with the approval processes for PCV13, PCV15 and PCV20 in infants, we do not anticipate that clinical field efficacy trials will be required for VAX-24 or VAX-31 in the pediatric population.

Our Phase 3 and commercial strategy for VAX-24 or VAX-31 for the infant indication will depend on several factors, including the results from our ongoing Phase 2 study for VAX-31. Pending the outcome of our Phase 2 VAX-31 study, we plan to initiate a Phase 3 program with an Optimized Dose formulation of VAX-24 or VAX-31. We expect our Phase 3 program in the pediatric population to focus on evaluating non-inferiority to PCV20, the current standard of care in infants, for immunogenicity and seroconversion or antibody concentration threshold; assessing U.S. routine vaccination responses following concomitant administration with our vaccine candidate; and generating a sufficient safety database in infants. The Phase 3 non-inferiority results would then be used to seek approval in the pediatric population. This approach is similar to the approach utilized to develop PCV13, where the immunogenicity of PCV13 was compared to the original 7-valent Prevnar product, which was the standard of care at the time, as well as the approaches for PCV15 and PCV20, which were compared to PCV13.

VAX-24

The VAX-24 Phase 2 infant study was a randomized, observer-blind, dose-finding two-stage clinical study evaluating the safety, tolerability and immunogenicity of VAX-24 at three dose levels, 1.1mcg, 2.2mcg, and 2.2mcg/ 4.4mcg, and compared to PCV15 and PCV20 in healthy infants. The Stage 1 portion of the study evaluated the safety and tolerability of a single injection of VAX-24 at three dose levels compared to PCV15 in 48 infants in a dose-escalation approach. The Stage 2 portion evaluated the safety, tolerability and immunogenicity of VAX-24 at three dose levels and compared to PCV20 in 789 healthy infants. In line with recommendations from the ACIP, the study design included a primary immunization series consisting of three doses given at two months, four months and six months of age, followed by a subsequent booster dose at 12-15 months of age. The key prespecified immunogenicity study endpoints included an assessment of immune responses for all three VAX-24 doses and compared to PCV20 on the shared serotypes measured at 30 days post-dose three (“PD3”) and post-dose four (“PD4”). Immune responses were assessed based on anti-pneumococcal polysaccharide serotype-specific IgG responses (proportion of participants achieving the accepted IgG threshold value of ≥0.35mcg/ml) at 30 days PD3 and IgG geometric mean titer ratios at 30 days PD4. All participants in the study were evaluated for safety through six months following the booster dose.

Figure 28 is a schematic of the overall study design of our VAX-24 infant Phase 2 study:

Figure 28.

In March 2025, we announced positive topline, interim data from the VAX-24 infant Phase 2 study and, in November 2025, we announced final safety, tolerability, and immunogenicity results that were consistent with the positive interim

data reported in March 2025 and showed that VAX -24 elicited robust, dose-dependent immune responses, with little to no evidence of carrier suppression observed. The final data analysis included full 6-month safety results and complete post-dose 3 (primary immunization series) and post-dose 4 (booster dose) IgG and OPA results. The key immunogenicity endpoints included an assessment of immune responses for each of the VAX-24 dose levels (Low, Mid, Mixed) in comparison with PCV20 for the 20 common and 4 unique serotypes in VAX-24. At 1-month post-dose 3 and post-dose 4, immune responses were assessed based on serotype-specific IgG seroconversion rates (IgG threshold value of ≥0.35mcg/mL). IgG GMRs were also assessed at 1-month post-dose 3 and post-dose 4, along with other key immunogenicity endpoints, including OPA.

Post-dose 3, all VAX-24 doses met target precedent Phase 2 non-inferiority (NI) criteria on relative seroconversion rates (lower limit of the 95% confidence interval for the difference between the proportion of participants achieving the pre-defined seroconversion rate (IgG concentration ≥0.35 mcg/mL) for the highest circulating serotypes, as defined by the percentage of IPD caused in individuals <5 yrs of age in the U.S. in 2023 based on ABC surveillance data, contained in VAX-24. The Low and Mid doses met the seroconversion rate criteria for 20 of 24 serotypes overall and the Mixed Dose met such criteria for 19 of 24 serotypes. The Mid and Mixed Doses met the target Phase 2 IgG GMR point estimate of >0.6 for 21 of 24 serotypes.

Post-dose 4, all VAX-24 doses met our target Phase 2 IgG GMR point estimate of >0.6 for the three highest circulating serotypes contained in VAX-24. The Mixed Dose met this target for 19 of 24 serotypes overall and the Mid dose met this target for 18 of 24 serotypes. Post-dose 4, VAX-24 elicited robust memory responses across all doses for all serotypes.

Additionally, the four incremental serotypes unique to VAX-24 that provide expanded serotype coverage relative to PCV20 elicited robust immune responses and met all target criteria across all endpoints at all doses evaluated.

In this study, VAX-24 was well-tolerated and demonstrated a safety profile similar to PCV20 across all doses studied. Frequently reported local and systemic reactions were generally mild-to-moderate, resolving within several days of vaccination, with no meaningful differences observed across the cohorts. No serious adverse events were considered to be related to study vaccines.

The final positive data from the VAX-24 infant Phase 2 dose-finding study further validated our rationale for exploring higher doses in the ongoing VAX-31 infant Phase 2 study.

VAX-31

The VAX-31 Phase 2 infant study is a randomized, double-blind, active controlled, dose-finding, three-stage clinical study evaluating the safety, tolerability and immunogenicity of VAX-31 compared to PCV20 in healthy infants. Stage 1 of the study evaluated the safety and tolerability of VAX-31 at three dose levels (Low, Middle and High) and compared to PCV20 in 48 infants in a dose-escalation approach. In the Low, Middle and High Doses, all serotypes were dosed at 1.1mcg, 2.2mcg and 3.3mcg, respectively, except serotypes 1, 5 and 22F, which were dosed at 1.65mcg, 3.3mcg, and

4.4mcg, respectively. Participants who received VAX-31 in Stage 1 continued the standard dosing regimen as part of Stage 2. Stage 2 is evaluating the safety, tolerability and immunogenicity of VAX-31 at the same three dose levels and compared to PCV20. In line with recommendations from the ACIP, the study includes a primary immunization series consisting of three doses given at two, four and six months of age, followed by a subsequent booster dose at 12-15 months of age. On September 2025, we announced advancement of the VAX-31 infant Phase 2 randomized, dose-finding study to the third and final stage following modifications to the protocol to add a new dose arm to evaluate the VAX-31 Optimized Dose (majority of serotypes dosed at 4.4mcg and the balance dosed at 3.3mcg) and discontinue enrollment in the Low Dose arm. The Middle and High Dose arms are continuing as planned.The key prespecified immunogenicity study endpoints include an assessment of immune responses for each of the VAX-31 dose levels in comparison with PCV20 for the 20 common and 11 unique serotypes in VAX-31. Post-primary series PD3 immune responses will be assessed based on serotype-specific IgG seroconversion rates (proportion of participants achieving the accepted IgG threshold value of ≥0.35mcg/mL) at 30 days PD3. IgG geometric mean titers will be assessed at 30 days PD3 and PD4, along with other key immunogenicity endpoints. All participants in the study will be evaluated for safety through six months following the booster dose.

Figure 29 is a schematic of the overall study design of our VAX-31 infant Phase 2 study:

Figure 29

We expect to announce topline safety, tolerability and immunogenicity data for the Phase 2 randomized, dose-finding study from the primary three-dose immunization series and booster dose either sequentially or together by the end of the first half of 2027.

Pending the VAX-31 infant study readout, we plan to initiate a Phase 3 program with an Optimized Dose formulation of VAX-24 or VAX-31.

Platform Application Two: Novel Conjugate Vaccine Opportunities

We are also developing novel conjugate vaccine candidates for other diseases for which there are no existing vaccines. By leveraging our platform, we have been able to generate novel protein carriers with site-specific incorporation of nnAAs designed to provide optimal exposure of both B-cell and T-cell epitopes on the carrier. Using these novel protein carriers, we can produce highly stable conjugate vaccine candidates through site-specific conjugation of antigens, including polysaccharides. Functionally, one significant advantage of using carriers may be the additional protective immunity that the protein itself can provide beyond the conjugated antigen itself.

Group A Strep Disease Background and Market Opportunity

Streptococcus pyogenes (S. pyogenes or Group A Strep) bacteria cause a wide spectrum of both acute and chronic clinical conditions that lead to considerable disease burden globally. Group A Strep causes an estimated 800 million cases of illness each year and is one of the leading infectious disease-related causes of death and disability worldwide. It is estimated that over 600,000 deaths globally result from Group A Strep, and, even in countries where antibiotic treatment is readily available, Group A Strep has a considerable disease burden contributing more than 600 million cases of pharyngitis per year along with substantial morbidity from cellulitis, invasive disease, and skin infections. The total annual market for a Group A Strep vaccine is estimated at approximately $3 billion to $4 billion globally. The annual economic burden of Group A Strep disease in the U.S. population is estimated to exceed $6 billion resulting from invasive disease and non-severe acute upper respiratory infections. In addition, Group A Strep drives significant antibiotic use, especially among children, and as such contributes towards increased antimicrobial resistance. Among older adults (≥ 65 years) in the United

States, rates of invasive disease and deaths caused by Group A Strep have been increasing over the last decade. Some of the most serious consequences of Group A Strep include invasive diseases such as flesh-eating disease (necrotizing fasciitis), sepsis and sequelae such as rheumatic heart disease ("RHD"). An estimated 55 million people are affected by RHD each year worldwide. Importantly, the majority of Group A Strep infections lead to pharyngitis, commonly known as strep throat, which is highly prevalent in school-age children. In the United States, an estimated 17% of outpatient antibiotic prescriptions dispensed to children aged 3 to 9 years are for the treatment of suspected Group A Strep infections. Studies have indicated that antibiotic resistance to Group A Strep has significantly increased over the past decade, leading the CDC to categorize Group A Strep as a concerning threat. Additionally, the development of vaccines against Group A Strep has become a priority for the WHO amid recognition of the rising disease incidence globally, as well as the need to combat avoidable antibiotic consumption.

It has been established that the repeated natural infection of children with Group A Strep results in immune responses that are protective against subsequent Group A Strep infection. We believe this observation justifies the development of a rationally designed vaccine for Group A Strep that is focused on conserved antigens expressed by all strains of the bacteria.

VAX-A1

We have developed a conjugate vaccine candidate, VAX-A1, designed to confer broad protection against subtypes of Group A Strep by virtue of polyrhamnose, a conserved polysaccharide, conjugated to Group A Strep specific immunogenic protein carrier using our site-specific conjugation technology. The resulting conjugate is designed to ensure optimal exposure of both the B-cell and T-cell epitopes on the protein carrier to confer robust, boostable and durable protective immune responses. We believe this single conjugate could potentially cover all Group A Strep strains. The vaccine is a combination of this novel protein-polysaccharide conjugate along with two additional conserved surface proteins.

Our initial preclinical proof-of-concept study was published in the journal Infectious Microbes & Diseases in December 2020. In the study, a novel protein and polysaccharide conjugate of the Group A Strep polysaccharide was constructed for inclusion in a universal subunit vaccine against infections by the pathogen. The VAX-A1 vaccine candidate, based on SpyAD-conjugated to a modified polyrhamnose backbone (lacking N-acetyl glucosamine) and including SLO and C5a peptidase, demonstrated protection from subcutaneous and systemic challenge in mice, antibody binding and opsonophagocytic killing for multiple Group A Strep M Protein Gene types and no evidence of cross-reactivity to human heart and brain tissue antigens (Figure 30), which is a key leading indicator of vaccine safety. The study was carried out in collaboration with researchers at the Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California School of Medicine and the Skaggs School of Pharmacy and Pharmaceutical Sciences at the University of California, San Diego.

Figure 30.

Our VAX-A1 vaccine development program has been funded in part by a grant obtained from Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator (“CARB-X”), a global non-profit partnership dedicated to accelerating antibacterial innovation to tackle the rising global threat of drug-resistant bacteria.

We nominated the final vaccine candidate for our VAX-A1 program and initiated IND-enabling activities in 2021 and plan to initiate a Phase 1 adult clinical study in 2026, with the primary objective of assessing safety and tolerability.

Platform Application Three: Protein Vaccine Opportunities

We believe we can also develop novel protein vaccine candidates constructed using “tough-to-make” protein antigens uniquely able to be expressed using the platform. In particular, the lack of a cellular membrane in our platform allows for the exogenous addition of components to manipulate transcription, translation and folding by modification of reaction conditions. Furthermore, removal of the typical restriction to maintain cell viability also creates unique avenues for optimizing and promoting protein production for antigens that might be cytotoxic to a cell-based system or require non-physiological conditions for optimal protein folding. Thus, utilizing these advantages, we believe we can express and purify important protein targets to generate unique candidates that are beyond the scope of traditional production systems.

VAX-GI

VAX-GI is a novel preclinical vaccine candidate being developed as a preventative treatment for dysentery and shigellosis, which is caused by Shigella bacteria. Shigella is a bacterial illness that causes dysentery with symptoms, including bloody diarrhea, fever, and stomach cramps. Currently there are no prophylactics and treatment is primarily oral rehydration therapy, with antibiotics (mainly ciprofloxacin and azithromycin) used to shorten the duration of infection. However, the growing incidence of antibiotic resistance has complicated this approach with an increasing rate of extensively drug resistant. Shigella is estimated to cause 80 million to 165 million cases of disease and 600,000 deaths annually, mostly among children. Further, in young children Shigella can cause malnutrition and induce or exacerbate stunting, leading to a long-term impact on both physical and cognitive development. This has resulted in the WHO including Shigella vaccine development as a priority goal.

VAX-GI, which includes cell-free produced IpaB conjugated to Shigella flexneri 2a polysaccharide was used to vaccinate mice which were evaluated for generation of a productive immune response and protection. All groups were challenged i.n. (pulmonary infection model) with virulent S. flexneri 2a 2457T or S. sonnei Moseley on day 57 postvaccination. Immunization with S. flexneri 2a OPS-IpaB conjugate vaccine afforded 78% protection against homologous S. flexneri 2a challenge (P < 0.0001) whereas S. flexneri 2a OPS-CRM provided only 50% protection (P = 0.0014) (Figure 33A). IpaB alone conferred 67% protection against S. flexneri 2a (P = 0.0003) (Figure 33A). The trend of higher protective efficacy of OPS-IpaB than of OPS-CRM or IpaB alone suggests that both OPS and IpaB contribute to the observed protective immunity. IpaB- and OPS-specific IgG titers in mice that were protected were significantly higher than titers in those that succumbed to infection (Figure 33C). Importantly, S. flexneri 2a OPS-IpaB exhibited 56% protection against heterologous S. sonnei challenge (P < 0.0001) (Figure 33B). Because Shigella O-polysaccharide immunity is serotype specific, this cross protection is attributable to IpaB. This is consistent with the lack of protection in the OPS-CRM group (11% survival). IpaB alone afforded 44% protection against S. sonnei (P = 0.0003) (Figure 33B), which was not significantly different from the protection elicited by S. flexneri 2a OPS-IpaB. IpaB-specific serum IgG was again significantly higher in mice that were protected against S. sonnei infection (Figure 33D). S. flexneri 2a and S. sonnei IpaBs share >98% homology; therefore, cross protection was expected. The slight difference in IpaB efficacy in the two experiments is likely due to the higher severity of S. sonnei infection (mice succumbed sooner). Unvaccinated control mice had very low to no survival. We plan to pursue conjugate and protein-only approaches simultaneously, as shown in Figure 34.

Figure 33.

Figure 34.

VAX-GI is being developed in collaboration with the University of Maryland, Baltimore as well as with partial funding from two research grants awarded by the NIH. As part of our continued focus on strategic capital deployment and in order to prioritize our resources towards our PCV franchise, we announced in August 2025 that we had paused the advancement, beyond preclinical development, of VAX-GI while remaining confident in its potential and preserving the option to advance the program in the future.

Manufacturing and Supply

We have designed and developed a proprietary, scalable and portable manufacturing process for VAX-31 and VAX-24 that we believe can scale to address clinical and commercial vaccine supply needed to serve both adult and pediatric populations.

VAX-31 and VAX-24 Process

The manufacturing process for our VAX-31 and VAX-24 vaccine candidates consists of four key components: (i) our proprietary eCRM protein carrier; (ii) the 31 or 24 pneumococcal polysaccharides; (iii) the 31 or 24 conjugate drug substances; and (iv) the mixture of these 31 or 24 drug substances into the final drug product.

eCRM

Our proprietary eCRM protein carrier is produced using our cell-free protein synthesis platform, which is exclusively licensed from Sutro Biopharma for the Vaccine Field (as defined in the Sutro Biopharma License Agreement (as defined below)). eCRM, contains multiple copies of non-native para azido-methyl-phenylalanine (“pAMF”) amino acid. The pAMF amino acids have a specific structure that enables eCRM to participate in the site-specific click chemistry conjugation reaction with activated pneumococcal polysaccharides.

The cell-free reaction is performed in a manner analogous to traditional fermentation but without the cells. The first step in the production of eCRM is the manufacture of critical raw materials, namely E. coli extracts and lysates that contain the cellular machinery required for in vitro DNA transcription and translation. The eCRM protein is then manufactured by combining these E. coli extracts and lysates with classic media components such as amino acids, minerals and salts, with the in vitro reaction driven by the addition of plasmid DNA coding for the eCRM protein’s amino acid sequence. This cell-free reaction takes place in a standard fermenter, followed by standard protein purification chromatographic and filtration processes. The manufacturing process has consistently yielded a product of the desired quality.

Pneumococcal Polysaccharides

Each of the 31 or 24 pneumococcal polysaccharides is individually isolated from Streptococcus pneumoniae bacterial strains. Each individual Streptococcus pneumoniae strain is cultured in a bioreactor using an improved single standardized fed-batch bioreactor process and a single standardized downstream purification process. Overall, this standardized upstream and downstream process is simple and streamlined, thereby reducing manufacturing cost of goods and providing an efficient path of progression for the program from process characterization and validation through to commercialization, if our vaccine candidates are approved.

Conjugate Drug Substances

Each of the 31 or 24 conjugate drug substances is manufactured individually, as monovalent conjugates, by conjugating each of the 31 or 24 activated pneumococcal polysaccharide strains, one at a time, to the eCRM carrier protein.

Click chemistry provides for a conjugation reaction that is quick, consistent and high-yielding, and which we optimized to be largely standardized across the various polysaccharides. Through statistical design of experiment studies, we have gained a significant understanding of which variables to adjust to maximize product quality and, accordingly, immunogenicity in rabbit models.

Drug Product

All 31 or 24 conjugate drug substances are mixed, formulated with appropriate excipients and adsorbed onto alum. Clinical doses are filled in vials and stored refrigerated.

Key Agreements

We currently do not own or operate any manufacturing facilities, but our strategic partnerships with Lonza and other contract manufacturing organizations (“CMOs”) provide us with access to substantial resources to facilitate an independent supply path to the market. We have entered into agreements with Lonza, a leading global contract manufacturer with deep domain expertise and experience in large and small-scale production of clinical, as well as commercial-stage products, to secure capacity, technical expertise and resources to support the production of eCRM, polysaccharides and drug substance for our PCV programs. We have also entered into a commercial manufacturing agreement with Lonza to support the potential global commercialization of our PCV candidates in both the adult and pediatric populations. This agreement complements our plans to utilize existing Lonza infrastructure to advance clinical development and the anticipated initial U.S. launch of VAX-31 for the adult population. We have relationships with other leading CMOs for the production of the final drug product for our PCV candidates, for the extract and lysates that we use to manufacture eCRM and for certain raw materials. We have an agreement with Sutro Biopharma pursuant to which Sutro Biopharma supplies us with extract and custom reagents for use in manufacturing preclinical and certain clinical supply of vaccine compositions. In December

2019, we exercised our right to require Sutro Biopharma to establish a second supplier for extract and custom reagents to support future clinical and commercial needs and thereafter initiated a tech transfer to a CMO as a second supplier of extract. In December 2022, we entered into a separate agreement with Sutro Biopharma pursuant to which we enhanced our rights with the second supplier of extract and acquired an option to access expanded rights to develop and manufacture extract, among other rights. In November 2023, we exercised this option and entered in a manufacturing rights agreement to obtain control over manufacturing and development of cell-free extract for our vaccine candidates. In September 2025, we announced a new agreement with Patheon Manufacturing Services, LLC, part of Thermo Fisher Scientific (collectively, "Thermo Fisher") to provide custom commercial fill-finish capacity for our broad-spectrum PCVs at Thermo Fisher's Greenville, North Carolina facility.

Lonza Agreements

Development and Manufacturing Services Agreements

In April 2022, we entered into a non-exclusive development and manufacturing services agreement with Lonza effective as of March 22, 2022, which was subsequently amended on May 12, 2022, November 21, 2022 and October 31, 2023 (as amended, the “2022 Lonza DMSA”). Pursuant to the 2022 Lonza DMSA, Lonza is obligated to perform services, including manufacturing process development and clinical manufacture and supply of our proprietary PCV candidates. Subject to the terms and conditions set forth in the 2022 Lonza DMSA, Lonza has granted to us a non-exclusive, worldwide, fully paid-up, irrevocable, transferable license, including the right to grant sublicenses, under the New General Application Intellectual Property, to research, develop, make, have made, use, sell and import the Product. Unless earlier terminated, the 2022 Lonza DMSA shall remain in place for a period of five years. Either party may terminate the 2022 Lonza DMSA for any reason on prior written notice to the other party, provided that Lonza may not exercise such right until a specified future date. In addition, either party may terminate the 2022 Lonza DMSA (i) within a given time period upon any material breach that is left uncured by the other party, or (ii) immediately if the other party becomes insolvent. We may also terminate the 2022 Lonza DMSA upon an extended force majeure event. Upon expiration and/or termination of the 2022 Lonza DMSA and/or any purchase order, we will pay Lonza for all service rendered, all costs incurred, all unreimbursed capital equipment and any cancellation fees (each term as defined in the 2022 Lonza DMSA).

In February 2023, we entered into another non-exclusive development and manufacturing services agreement with Lonza effective as of March 1, 2023 (the “2023 Lonza DMSA”). Pursuant to the 2023 Lonza DMSA, Lonza will perform manufacturing process development and the manufacture of components for our PCV candidates, including the polysaccharide antigens, our proprietary eCRM protein carrier and conjugated drug substances. Subject to the terms and conditions set forth in the 2023 Lonza DMSA, Lonza has granted to us a non-exclusive, worldwide, fully paid-up, transferable license, including the right to grant sublicenses (subject to the prior written consent of Lonza), under the New General Application Intellectual Property, to use, sell and import the Product manufactured under the 2023 Lonza DMSA (but no other products). Unless earlier terminated, the 2023 Lonza DMSA shall remain in place for a period of five years and shall automatically renew for one additional two-year period unless either party provides written notice of non-renewal at least two years prior to the fifth anniversary of the effective date. We may terminate the 2023 Lonza DMSA for any reason on prior written notice to the other party on a Project Plan-by-Project Plan basis. Either party may terminate the 2023 Lonza DMSA (i) within a given time period upon any material breach that is left uncured by the other party, (ii) immediately if the other party becomes insolvent, is dissolved or liquidated, makes a general assignment for the benefit of its creditors, or files or has filed against it, a petition in bankruptcy or has a receiver appointed for a substantial part of its assets, (iii) upon an extended force majeure event, or (iv) if it becomes apparent to either party at any stage in the provision of the Services that it will be impossible to complete the Services for scientific or technical reasons despite exercise of best commercial efforts by both parties. Pursuant to the reason for termination and the party initiating the termination, we will pay Lonza for some combination of services rendered, costs incurred, unreimbursed capital equipment and/or any cancellation fees. Upon an extended force majeure event, neither party shall have any further liability to the other party (each term as defined in the 2023 Lonza DMSA).

Under each of the 2022 Lonza DMSA and 2023 Lonza DMSA (collectively, the “Lonza Agreements”), we pay Lonza agreed-upon fees for their performance of development and manufacturing services and pass-through expenses incurred by Lonza for raw materials, as well as customary procurement and handling fees. Under each Lonza Agreement, we own all rights, title and interest in and to any and all New Customer Intellectual Property (as defined in each Lonza Agreement), and Lonza owns all rights, title and interest in New General Application Intellectual Property (as defined in each Lonza Agreement).

Commercial Manufacturing and Supply Agreement

On October 13, 2023, we entered into a pre-commercial services and commercial manufacturing supply agreement with Lonza (the “Lonza Commercial Manufacturing and Supply Agreement”).

Pursuant to the Commercial Manufacturing and Supply Agreement, Lonza will (i) construct and build out a dedicated suite (the “Suite”) at Lonza’s facilities in Visp, Switzerland to manufacture certain key components (including drug substance) for our proprietary PCV franchise and any other products or intermediates we may choose (collectively, the “Products”) and (ii) maintain and operate the Suite (utilizing Lonza’s employees) to manufacture the Products as a service provided to us, including conducting related quality control and quality assurance operations. Lonza will be a preferred, non-exclusive, supplier of the Products to us, and we retain the right to procure the Products from one or more alternate and/or backup manufacturers of the Products (including at our own facilities).

Under the Lonza Commercial Manufacturing and Supply Agreement, prior to completion of construction and certification of the Suite for commercial operation, we will contribute to the capital expenditure costs to construct the Suite (and will own certain equipment in the Suite to be purchased or otherwise acquired by us), and will pay Lonza a fixed-rate monthly service fee for Lonza’s pre-commercial services prior to commencement of commercial operations (which monthly service fee amount is subject to increases in subsequent years). Following commencement of commercial operations of the Suite to manufacture the Products, we will pay Lonza (i) Suite fees based on allocations of certain of Lonza’s costs to maintain the facility in which the Suite is located and to provide shared services to us and Lonza’s other customers in such facility, (ii) service fees based upon Lonza’s actual full-time equivalent employee (“FTE”) costs to operate the Suite to manufacture the Products, and (iii) certain other pass-through costs, including for raw materials. In addition, we may be obligated to pay or reimburse Lonza for certain other fees and expenses under the Lonza Commercial Manufacturing and Supply Agreement. Lonza will be eligible for certain financial bonuses, and subject to certain financial penalties, as incentives for the timely completion of certain scale-up activities, receipt of certain regulatory approvals for the Suite and manufacture of the Products in accordance with our commercial requirements.

Unless earlier terminated, the Lonza Commercial Manufacturing and Supply Agreement will remain in effect until December 31, 2038, subject to automatic renewal for up to three additional renewal periods of five years each, unless we elect not to renew (with 24 months advanced notice to Lonza). We are permitted to terminate the Lonza Commercial Manufacturing and Supply Agreement for convenience or for Lonza’s uncured material breach, in each case subject to certain notice obligations. Lonza is permitted to terminate the Commercial Manufacturing and Supply Agreement in the event that we commit certain specified material breaches, including uncured failure to pay material, undisputed amounts of money due to Lonza, subject to certain notice obligations. Either party may terminate the Commercial Manufacturing and Supply Agreement in certain circumstances in the event of the other party’s bankruptcy. In the event that we terminate the agreement for convenience, or Lonza terminates the agreement in the event that we commit certain specified material breaches, then certain termination consequences may be triggered, including that (i) we would forfeit any outstanding entitlement to credit from Lonza of the Repurposing Fee (as defined below), and (ii) we would be obligated to pay Lonza a termination penalty equal to the greater of (a) CHF 70.0 million, or (b) a prespecified number of months’ FTE fees for the actual FTEs assigned to us as of the date of termination. Within 30 days of the Effective Date, we paid Lonza a repurposing fee (the “Repurposing Fee”) of CHF 27.0 million that will be credited back to us over a 10-year period starting upon commencement of commercial production. In the event of termination under certain circumstances, Lonza shall be obligated to provide certain wind-down and transition services to us for up to 12 and 24 months, respectively.

2026 Development and Manufacturing Services Agreement

On February 18, 2026, we entered into a development and manufacturing services agreement with Lonza, effective as of January 1, 2026, pursuant to which Lonza will perform manufacturing process development and commercial manufacture and supply of certain key components for our proprietary PCV franchise. Under the agreement, we will pay Lonza for development and manufacturing services, in addition to paying for certain raw material and other costs. We will be required to purchase, and Lonza will be required to supply, the components pursuant to the relevant purchase orders under the agreement. In consideration of the commercial supply services and Lonza’s other obligations under the agreement, we will pay Lonza a daily fee for Lonza’s operation of the facility solely to actively manufacture the components. With respect to such commercial supply, and subject to termination rights, we and Lonza have agreed to a mutually binding percentage of annual facility capacity that shall be utilized by Lonza fully and exclusively for Lonza’s performance of services thereunder, which percentages may be adjusted under certain circumstances.

Unless earlier terminated, the agreement will remain in effect until December 31, 2038, subject to automatic renewal for up to three additional renewal periods of five years each, unless we elect not to renew. We may terminate the agreement for convenience, and the agreement contains customary for-cause termination rights for each party. If the Agreement is

terminated (i) by us for convenience, or (ii) by Lonza for our uncured failure to pay material, undisputed amounts of money due to Lonza, then we shall pay Lonza certain cancellation fees as specified in the agreement.

Sutro Biopharma Agreements

Amended and Restated License Agreement

We are party to an amended and restated license agreement with Sutro Biopharma, dated October 12, 2015, which was subsequently amended on May 9, 2018, May 29, 2018, September 28, 2023 and November 21, 2023 (as amended, the “Sutro Biopharma License Agreement”). Under the Sutro Biopharma License Agreement, we received an exclusive, worldwide, royalty-bearing, sublicensable license under Sutro Biopharma’s patents and know-how relating to cell-free expression of proteins to (i) research, develop, use, sell, offer for sale, export, import and otherwise exploit specified vaccine compositions, such rights being sublicensable, for the treatment or prophylaxis of infectious diseases, excluding cancer vaccines, and (ii) manufacture, or have manufactured by an approved contract manufacturing organization, such vaccine compositions from extracts supplied by Sutro Biopharma pursuant to the Sutro Biopharma Supply Agreement (as described below). We are obligated to use commercially reasonable efforts to develop, obtain regulatory approval for and commercialize the vaccine compositions. In consideration of the rights granted under the Sutro Biopharma License Agreement, we are obligated to pay Sutro Biopharma a 4% royalty on worldwide aggregate annual net sales of our vaccine products for human health and a 2% royalty on such net sales of vaccine products for animal health. Such royalty rates are subject to specified reductions, including standard reductions for third-party payments and for expiration of relevant patent claims. We are also obligated to pay Sutro Biopharma any royalties due to Stanford University (the upstream licensor of Sutro Biopharma), to the extent the royalties payable by Sutro Biopharma to Stanford University are greater than the royalties payable by us to Sutro Biopharma. Royalties are payable on a vaccine composition-by-vaccine composition and country-by-country basis until the later of expiration of the last valid claim in the licensed patents covering such vaccine composition in such country and 10 years after the first commercial sale of such vaccine composition. The latest expiration date of a licensed Sutro Biopharma patent application, if issued, would be 2036, subject to any adjustment or extension of patent term that may be available in a particular country. In addition, we are obligated to pay Sutro Biopharma a percentage of net sublicensing revenue received in the low teen percentages. In addition, in the event we sublicense our non-manufacturing rights under the Sutro Biopharma License Agreement before a specified date, we are obligated to pay Sutro Biopharma a percentage, in the low double-digits, of the sublicensing revenue we receive under such agreement.

On September 28, 2023, we and Sutro Biopharma amended certain terms of the Sutro Biopharma License Agreement, including with respect to (i) royalty reduction provisions applicable in the event of expiration of relevant patent claims, which would result in lower royalties payable by us to Sutro Biopharma under certain circumstances, (ii) the ownership, prosecution, maintenance and enforcement of certain intellectual property rights licensed or arising under the Sutro Biopharma License Agreement (including as agreed to be amended in the Option Agreement (as defined below), and (iii) the timing and form for financial reporting of royalty payment calculations.

The Sutro Biopharma License Agreement will remain in effect until terminated. The agreement may be terminated by either party for the other party’s material breach uncured within 60 days’ notice, by us at will with 60 days’ notice, or by Sutro Biopharma if we challenge Sutro Biopharma’s patents or if we undergo a change of control with a specified competitor of Sutro Biopharma.

Supply Agreement

In May 2018, we entered into a supply agreement with Sutro Biopharma, which was subsequently amended on February 22, 2021 and November 21, 2023 (as amended, the “Sutro Biopharma Supply Agreement”) pursuant to which we purchase from Sutro Biopharma extract and custom reagents for use in manufacturing non-clinical and certain clinical supply of vaccine compositions utilizing the technology licensed under the Sutro Biopharma License at prices not to exceed a specified percentage above Sutro Biopharma’s fully burdened manufacturing cost. If any extracts or custom reagents do not meet the specifications and warranties provided, then we will not have an obligation to pay for the non-conforming product, and Sutro Biopharma will be obligated to replace the non-conforming product within the shortest possible time with conforming product at our cost. The term of the Sutro Biopharma Supply Agreement is from execution until the later of (i) July 31, 2022, or (ii) the date that we and Sutro Biopharma enter into the Phase 3/Commercial Supply Agreement and Sutro Biopharma is supplying to us each Product under the Phase 3/Commercial Supply Agreement (each term as defined in the Sutro Biopharma Supply Agreement). The Sutro Biopharma Supply Agreement may be terminated by either party for the other party’s material breach uncured within 60 days’ notice, by us at will with 60 days’ notice, or by mutual agreement of the parties. In December 2019, we exercised our right to require Sutro Biopharma to establish a second supplier for extract and custom reagents to support our anticipated clinical and commercial needs.

Option Agreement

In December 2022, we entered into an option grant agreement with Sutro Biopharma (the “Option Agreement”). Pursuant to the Option Agreement, we acquired from Sutro Biopharma (i) authorization to enter into an agreement with an independent alternate CMO to directly source Sutro Biopharma’s cell-free extract, allowing us to have direct oversight over financial and operational aspects of the relationship with the CMO; and (ii) a right, but not an obligation, to obtain certain exclusive rights to internally manufacture and/or source extract from certain CMOs and the right to independently develop and make improvements to extract (including the right to make improvements to the extract manufacturing process as well as cell lines) for use in connection with the exploitation of certain vaccine compositions (the “Option”). We and Sutro Biopharma agreed to negotiate the terms and conditions of a form definitive agreement to be entered into in the event we exercise the Option, which would include the terms and conditions set forth in an executed term sheet between us (the “Term Sheet”) and such terms that were necessary to give effect to each of the terms and conditions set forth in the Term Sheet (the “Form Definitive Agreement”).

As consideration for the Option and other rights and authorizations granted to us under the Option Agreement, we paid Sutro Biopharma upfront consideration of $22.5 million, consisting of (i) $10.0 million in cash and $7.5 million worth of shares of our common stock (the number of shares calculated based on the arithmetic average of the daily volume weighted average price of our common stock as traded on Nasdaq in the three consecutive trading days immediately prior to the issuance thereof) in December 2022, and (ii) $5.0 million in October 2023 within five business days after we and Sutro Biopharma mutually agree in writing upon the Form Definitive Agreement on September 28, 2023. The 167,780 shares of common stock issued was recorded at fair value of $8.0 million on the date of settlement, December 22, 2022.

On November 21, 2023 (the “Option Exercise Date”), we exercised the Option by submitting written notice thereof to Sutro Biopharma and concurrently paid Sutro Biopharma $50.0 million in cash as the first of two installment payments for the Option exercise price, followed by the second and final installment of $25.0 million in cash in May 2024. Upon the occurrence of certain regulatory milestones, certain additional milestone payments may total up to $60.0 million in cash. In the event that we undergo a change of control, certain rights and payments may be accelerated.

Manufacturing Rights Agreement

Concurrent with the payment of the first installment of the Option exercise price pursuant to the Option Agreement, on November 21, 2023, the manufacturing rights agreement (in the form of the Form Definitive Agreement) between us and Sutro Biopharma (the “Manufacturing Rights Agreement”) became effective. Under the Manufacturing Rights Agreement, we received an exclusive (except as to Sutro Biopharma), perpetual (subject to termination), worldwide license, for no additional royalty (i.e., royalty-free, other than any royalties due under the Sutro Biopharma License Agreement), under Sutro Biopharma’s relevant patents and know-how, to manufacture or have manufactured extract and improvements to extract (in any form) solely for use in the research, development, use, production, sale, offering for sale, export, import, commercialization or other exploitation of Vaccine Compositions (as defined in the Sutro Biopharma License Agreement) (as well as certain rights with respect to certain regulatory matters related to extract and its use in connection with such Vaccine Compositions). We have the right to extend our rights and obligations under the Manufacturing Rights Agreement to our affiliates and to sublicense our rights to manufacture extract and improvements to extract to certain third-party CMOs and other contractors (for our benefit and not for such third party’s independent commercial use). For clarity, we are not permitted to manufacture extract for sale to third parties for the independent use of such third parties. Under the Manufacturing Rights Agreement, we have the obligation to protect the confidentiality of the extract manufacturing technology, and Sutro Biopharma has certain audit rights in connection therewith.

Under the Manufacturing Rights Agreement, upon our request and at our cost, Sutro Biopharma will support up to two technology transfers to us (or to an affiliate of ours or certain third-party CMOs designated by us) of certain Sutro Biopharma know-how, materials and information to enable us to manufacture or have manufactured extract. Under certain circumstances, Sutro Biopharma may source extract from us or certain third-party CMOs, subject to reimbursement for technology transfer costs.

The Manufacturing Rights Agreement contains certain terms with respect to the ownership, prosecution, maintenance and enforcement of certain intellectual property rights licensed or arising under the Manufacturing Rights Agreement, which are generally consistent with the Sutro Biopharma License Agreement.

Unless earlier terminated, the Manufacturing Rights Agreement will remain in effect in perpetuity. Sutro Biopharma may only terminate the Manufacturing Rights Agreement in the event of our (i) uncured, intentional, material breach of certain confidentiality provisions resulting in actual, material harm to Sutro Biopharma’s business, (ii) uncured, intentional material breach of certain provisions relating to the use of certain of Sutro Biopharma’s know-how outside of the Vaccine Field, (iii) unintentional, material breach of certain provisions relating to the use of certain of Sutro Biopharma’s know-

how outside of the Vaccine Field that we do not use reasonable best efforts to cease and (to the extent reasonably curable) cure in a timely fashion, or (iv) uncured failure to pay the Option exercise price or any undisputed milestone payment under the Option Agreement when due. We may terminate the Manufacturing Rights Agreement at our discretion upon 60 days’ written notice, and both parties may terminate the Manufacturing Rights Agreement upon mutual written consent.

Thermo Fisher Scientific Agreement

Commercial Manufacturing and Supply Agreement

In September 2025, we entered into a master services agreement with Thermo Fisher, pursuant to which Thermo Fisher will formulate, fill, inspect, package, label, test, manufacture and supply drug product for us at Thermo Fisher’s facility in Greenville, North Carolina (the "Thermo Fisher Commercial Manufacturing and Supply Agreement"). Pursuant to the Thermo Fisher Commercial Manufacturing and Supply Agreement, we have agreed to order drug product from Thermo Fisher based on certain binding forecast periods and established prices. In addition, we will also pay Thermo Fisher for technology transfer activities and reimburse Thermo Fisher for certain out-of-pocket capital expenditures under the terms of the agreement.

The Thermo Fisher Commercial Manufacturing and Supply Agreement has an initial term of 15 years and will automatically renew for additional three-year periods unless either party provides notice of non-renewal before the end of the then existing term, subject to completion of ongoing services. We are permitted to terminate the Thermo Fisher Commercial Manufacturing and Supply Agreement prior to expiration, subject to the payment of applicable termination fees, plus certain capital expenditure commitments.

University of California, San Diego License Agreement

We are party to a license agreement with the University of California, San Diego, dated February 4, 2019, which was subsequently amended on August 16, 2019 (as amended, the “UCSD License”) whereby we are the exclusive licensee of an issued U.S. patent and pending U.S. patent application related to a non-cross-reactive Group A Strep carbohydrate antigen and methods of producing the antigen. We licensed this technology for the development of our Group A Strep vaccine candidate.

Upon execution of the UCSD License, we made an upfront payment of $10,000, and each year during the term we are obligated to pay an annual license maintenance fee in the single digit thousands. We are also obligated to pay UCSD up to approximately $1 million in development and regulatory milestone payments for each licensed product under the agreement. Additionally, we are obligated to pay UCSD a fixed royalty on net sales of licensed products in the low single digits. Such royalty rate is subject to standard reductions for third-party payments. Royalties are payable until expiration of the last licensed patent. Additionally, in the event we sublicense commercial rights under the UCSD License, we are obligated to pay UCSD a percentage of all sublicensing revenue received, excluding any earned royalties or reimbursements of research and development expenses, of 20% up to a maximum of $2.5 million.

We are obligated to use commercially reasonable efforts to diligently develop, manufacture and sell licensed products and to achieve specified research and clinical development milestone events. If we are unable to meet our diligence obligations and do not agree with UCSD to modify such obligations or do not cure such obligations, then UCSD may terminate the license or convert the license to non-exclusive.

The UCSD License will remain in effect until the expiration of the last licensed patent. The UCSD patent and patent application, if issued, would expire in 2032, subject to any adjustment or extension of patent term that may be available in the United States. The UCSD License may be terminated by us at will with 90 days’ notice or by UCSD for our breach uncured within 90 days’ notice or if we challenge the licensed patents.

Other Partners

In addition to those listed above, we seek to partner with various academic, governmental and public or private research institutions as needed to advance the discovery or development of our vaccine candidates.

Competition

In recent history, the global vaccine market has been highly concentrated among a small number of multinational pharmaceutical companies. Pfizer, Merck, GSK and Sanofi have been responsible for developing and introducing most new vaccines to the world. Other pharmaceutical and biotechnology companies, academic institutions, governmental

agencies and public and private research institutions are also working towards new solutions given the continuing global unmet medical need.

Within the current pneumococcal vaccine market, Pfizer, Merck and GSK have comprised the significant majority of market share and sales, with Pfizer’s PCV13 and PCV20, Merck’s PPSV23, PCV15 and PCV21 and GSK’s Synflorix totaling a combined $8.5 billion in global pneumococcal vaccine sales in 2025 (approximately 77%, 21% and 2%, of such sales for these three product families, respectively).

Existing vaccine makers, as well as new entrants, are competing to develop the next generation of pneumococcal vaccines. PCV20 was granted regulatory approval and launched in the U.S. in 2021 for the prevention of IPD and pneumonia in adults, and in 2023, the FDA approved PCV20 for use in infants for the prevention of IPD, and for the prevention of otitis media caused by Streptococcus pneumoniae serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F. PCV15 was granted regulatory approval and launched in the U.S. in 2021 for the prevention of IPD in adults, and in 2022, the FDA approved PCV15 for use in infants for the prevention of IPD. PCV21 was granted regulatory approval and launched in the U.S. in 2024 for the prevention of IPD and pneumonia (serotypes 3, 6A, 7F, 8, 9N, 10A, 11A, 12F, 15A, 15C, 16F, 17F, 19A, 20A, 22F, 23A, 23B, 24F, 31, 33F, and 35B) in adults. The indications for the prevention of pneumonia for both PCV20 and PCV21 are approved under accelerated approvals based on immune responses as measured by OPA.

The current standard-of-care in adults consists of the administration of either PCV20 or PCV21 alone or PCV15 followed by the administration of PPSV23. In infants, the current standard-of-care consists of the administration of either PCV20 or PCV15 alone.

Pfizer announced in 2024 that it is developing a 25-valent PCV candidate that is currently in adult and pediatric Phase 2 clinical trials, and that it is working on a 30-plus valent PCV candidate that is in preclinical development. Pfizer announced in November 2025 that it plans to initiate adult and pediatric pivotal trials evaluating PCV25 in 2026.

In September 2025, Merck announced positive results from its Phase 3 study evaluating PCV21 in children aged 2–17 with increased risk for pneumococcal disease. Merck is also advancing additional next-generation PCV candidates through multiple early-phase clinical studies evaluating different formulations.

GSK, which previously acquired vaccine developer Affinivax, was previously developing a 24‑valent affinity‑bound pneumococcal vaccine candidate in adults and infants. In October 2024, GSK announced the termination of its adult 24-valent program in favor of a preclinical 30-plus valent candidate. In October 2025, GSK announced the initiation of a Phase 1 study in Australia evaluating its 30-plus valent candidate in adults. In the fourth quarter of 2025, GSK removed its pediatric 24-valent candidate, which had previously advanced into a Phase 2 clinical trial program, from its publicly disclosed pipeline.

Sanofi and SK bioscience have partnered to develop a 21-valent PCV and, in June 2023, announced positive results from their Phase 2 clinical trials in infants. In December 2024, Sanofi and SK bioscience announced the initiation of a global pediatric Phase 3 clinical program of their 21-valent PCV candidate, as well as an expanded agreement to develop, license and commercialize "next-generation" PCVs for both pediatric and adult populations. In February 2026, SK bioscience announced that it expected topline results from this Phase 3 study to be available in 2027, and that a next-generation PCV candidate, also co-developed with Sanofi, was in preclinical development with clinical trial entry expected in 2026.

We believe success will ultimately be based on the combination of several factors, including the broadest coverage of serotypes, disease coverage, immunogenicity, boostability, safety and tolerability. Convenience and pricing may also be factors. Other vaccines in development may obtain FDA approval and commercially launch before VAX-31 or VAX-24. However, if approved, we believe, based on our clinical results to-date and our unique site-specific conjugation and carrier-sparing technology, that our PCV candidates may potentially replace the current standard-of-care vaccines for IPD prevention in both the adult population, in the case of VAX-31, and pediatric population, in the case of VAX-24 and/or VAX-31.

The competitive landscape for vaccine development for Group A Strep was dormant for more than three decades. However, the FDA lifted a 30-year ban on Group A Strep vaccine clinical trials in 2005, and research has slowly started to resurface, mostly in academic institutions. Based on publicly available information, a limited number of Group A Strep vaccine candidates are in development, including programs at the GSK Vaccines Institute for Global Health which is in a preclinical stage, Moderna which has a candidate in a Phase 1 study, and Griffith University which has an ongoing Phase 1/2 clinical study in healthy adults, as well as other early-stage efforts including VaxForm and BioMVis that have been described as preclinical or otherwise early in development. We are not aware of any Group A Strep vaccine candidate in clinical development that is designed to provide broad coverage across all Group A Strep strains. Competition in this area is expected to be based on clinical profile and development progress, including potential efficacy, safety and tolerability,

dosing regimen and convenience, manufacturing feasibility, and pricing and access dynamics. In addition, we are aware that some companies are developing therapeutic approaches for Group A Strep-associated diseases that may overlap with certain clinical or commercial segments targeted by Group A Strep vaccines.

Based on publicly available information, we are aware of a limited number of Shigella vaccine programs in clinical development, including candidates being advanced by Valneva and LimmaTech. In addition, we are aware that some companies are developing therapeutics for other indications that target pathogens or biological mechanisms that may overlap with the underlying pathogens associated with Shigella, which could compete in certain patient populations or clinical settings. Competition in this area is expected to be based on clinical profile and development progress, including potential efficacy, safety and tolerability, dosing regimen and convenience, manufacturing feasibility, and pricing and access dynamics.

Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize vaccines that are safer, more effective, more convenient, less expensive or with a more favorable label than VAX-31, VAX-24 or any other vaccine we may develop. Many of the companies against which we compete have significantly greater financial resources, and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approvals and marketing approved drugs than we do.

Intellectual Property

We have developed, and are continuing to develop, a comprehensive intellectual property portfolio related to vaccine applications, including manufacturing, formulation and process applications as well as protection for our specific vaccine candidates.

Our success depends in part on our ability to obtain and maintain proprietary protection for our vaccine candidates, technology and know-how, to operate without infringing the proprietary rights of others and to prevent others from infringing our proprietary rights. Our policy is to seek to protect our proprietary position by, among other methods, pursuing and obtaining patent protection in the United States and in jurisdictions outside of the United States related to our proprietary technology, inventions, improvements and vaccine candidates that are important to the development and implementation of our business. Our patent portfolio is intended to cover our vaccine candidates and components thereof, their methods of use and processes for their manufacture and any other inventions that are commercially important to our business. We may also rely on trademarks, trade secrets and know-how to develop and maintain our proprietary position.

Generally, issued patents are granted a term of 20 years from the earliest claimed non-provisional filing date. In certain instances, patent term can be adjusted to recapture a portion of delay by the U.S. Patent and Trademark Office (“USPTO”) in examining the patent application or extended to account for term effectively lost as a result of the FDA regulatory review period, or both. In addition, we cannot provide any assurance that any patents will be issued from our pending or future applications or that any issued patents will adequately protect our vaccine candidates.

Our patent portfolio as of February 24, 2026 contains four issued U.S. patents and multiple issued international patents, multiple pending patent applications in the United States and internationally, and multiple pending patent cooperation treaty applications that are owned by us, as well as certain foreign counterparts of a subset of these patent applications in foreign countries, including Australia, Brazil, Canada, China, India, Israel, Japan, South Korea, Taiwan, Mexico, New Zealand, the Philippines, Singapore, South Africa and countries within the European Patent Convention and the Eurasian Patent Organization. For our pneumococcal vaccines, these patent applications are directed to vaccine formulations, protein-antigen conjugates, methods of making protein-antigen conjugates and other processes related to vaccine production, and the promotion of immunogenicity using the protein-antigen conjugates and vaccines. For our Group A Strep vaccine, these patent applications are directed to vaccine formulations, protein-antigen conjugates, vaccines and components thereof, as well as processes for their manufacture. If issued, the 20-year term expiration dates of our patents will expire between 2037 and 2043, not including any extension of the patent term that may be available in certain jurisdictions. We continue to seek to maximize the scope of our patent protection for all our programs.

In addition to patents, we also rely upon trademarks, trade secrets, know-how and continuing technological innovation to develop and maintain our competitive position. We maintain and are seeking both registered and common law trademarks. Common law trademark protection typically continues where and for as long as the mark is used. Registered trademarks continue in each country for as long as the trademark is registered. We believe that we have certain know-how and trade secrets relating to our technology and vaccine candidates. We rely on trade secrets to protect certain aspects of our technology related to our current and future vaccine candidates. However, trade secrets can be difficult to protect. We seek to protect our proprietary information, including trade secrets, in part, by using confidentiality agreements with our commercial partners, collaborators, employees and consultants, and invention assignment agreements with our employees. We also have confidentiality agreements or invention assignment agreements with our commercial partners and selected

consultants. These agreements may be breached, and we may not have adequate remedies for any breach. In addition, our trade secrets may otherwise become known or be independently discovered by competitors. We also seek to preserve the integrity and confidentiality of our data and trade secrets by maintaining the physical security of our premises and physical and electronic security of our information technology systems. To the extent that our commercial partners, collaborators, employees and consultants use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions.

Obtaining patents does not guarantee our right to practice the patented technology or commercialize the patented product. Third parties may have or obtain rights to patents that could be used to prevent or attempt to prevent us from commercializing our vaccine candidates. If third parties prepare and file patent applications in the United States or other jurisdictions that also claim technology to which we have rights, we may have to participate in interference or derivation proceedings in the USPTO or similar proceedings in other jurisdictions to determine the priority of invention.

Coverage and Reimbursement

Sales of our products in the United States will depend, in part, on the extent to which the costs of the products are covered by third-party payors, such as government health programs, commercial insurance and managed health care organizations. The process for determining whether a third-party payor will provide coverage for a pharmaceutical or biological product is typically separate from the process for setting the price of such a product or for establishing the reimbursement rate that the payor will pay for the product once coverage is approved. As a result, a third-party payor’s decision to provide coverage for a pharmaceutical or biological product does not imply that the reimbursement rate will be adequate. Certain Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act of 2010 (collectively, the “ACA”) marketplace and other private payor plans are required to include coverage for certain preventative services, including vaccinations recommended by the ACIP without cost share obligations (i.e., co-payments, deductibles or co-insurance) for plan members. Children through 18 years of age without health insurance coverage for vaccines may be eligible to receive such vaccinations free-of-charge through the CDC’s Vaccines for Children program (“VFC”). For Medicare beneficiaries, vaccines may be covered under either the Part B program or Part D depending on several criteria, including the type of vaccine and the beneficiary’s coverage eligibility.

Further, no uniform policy for coverage and reimbursement exists in the United States, and coverage and reimbursement can differ significantly from payor to payor. Third-party payors often rely upon Medicare coverage policy and payment limitations in setting their own reimbursement rates, but also have their own methods and approval process apart from Medicare determinations. As such, one third-party payor’s decision to cover a particular medical product or service does not ensure that other payors will also provide coverage for the medical product or service or will provide coverage at an adequate reimbursement rate. Further, coverage policies and third party reimbursement rates may change at any time. Even if favorable coverage and reimbursement status is attained for one or more products that receives regulatory approval, less favorable coverage policies and reimbursement rates may be implemented in the future.

Government Regulation

Government authorities in the United States, at the federal, state and local level, and other countries extensively regulate, among other things, the research, development, testing, safety, effectiveness, manufacture, quality control, approval, post-approval monitoring and reporting, labeling, packaging, storage, record-keeping, promotion, advertising, distribution, marketing and export and import of products such as those we are developing. A new biological product must be licensed by the FDA through a BLA, before it may be legally marketed in the United States.

In the United States, pharmaceutical products are regulated by the FDA under the Federal Food, Drug and Cosmetic Act and other laws, including, in the case of biologics, the Public Health Service Act (the “PHS Act”).

Failure to comply with FDA requirements, both before and after product approval, may subject us or our partners, contract manufacturers and suppliers to administrative or judicial sanctions, including FDA refusal to approve applications, warning letters, product recalls, product seizures, total or partial suspension of production or distribution, fines and/or criminal prosecution.

The steps required before a biologic may be approved for marketing of an indication in the United States generally include:

•completion of preclinical laboratory tests, animal studies, formulation studies conducted in accordance with good laboratory practices and other applicable regulations;

•submission to the FDA of an IND application, which must be active before human clinical trial commencement;

•approval by an institutional review board (“IRB”) or ethics committee at each clinical site before a clinical trial is commenced;

•completion of adequate and well-controlled human clinical trials in accordance with good clinical practice (“GCP”) requirements to establish that the biological product is “safe, pure and potent,” which is analogous to the safety and efficacy approval standard for a chemical drug product for its intended use;

•preparation and submission to the FDA of a BLA for marketing approval that includes substantive evidence of safety, purity and potency from results of nonclinical testing and clinical trials;

•a determination by the FDA within 60 days of its receipt of a BLA to file the application for review;

•satisfactory completion of an FDA pre-approval inspection of the manufacturing facility or facilities at which the product is produced to assess compliance with applicable current good manufacturing practices (“cGMP”) to assure that the facilities, methods and controls are adequate to preserve the products identify, strength, quality and purity;

•potential FDA audit of the nonclinical and clinical trial sites that generated the data in support of the BLA; and

•FDA review of the BLA and issuance of a biologics license, which is the approval necessary to market a vaccine.

Before conducting studies in humans, laboratory evaluation of product chemistry, toxicity and formulation, and other nonclinical studies must be conducted. Preclinical toxicology studies in animals must be conducted in compliance with applicable federal regulations and requirements, including good laboratory practices and the Animal Welfare Act and its implementing regulations.

The results of the preclinical tests, together with manufacturing information, known as CMC, and analytical data, are submitted to the FDA as part of an IND application. Some preclinical testing may continue even after the IND application is submitted. In addition to including the results of the preclinical testing, the IND application will also include a protocol detailing, among other things, the objectives of the clinical trial, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated if the first phase or phases of the clinical trial lend themselves to an efficacy determination. The IND application will automatically become effective 30 days after receipt by the FDA unless the FDA within the 30-day time period places the IND application on clinical hold because of safety concerns about the vaccine candidate or the conduct of the trial described in the clinical protocol included in the IND application. The IND application sponsor and the FDA must resolve any outstanding concerns before clinical trials can begin. Submission of an IND application therefore may or may not result in FDA authorization to begin a clinical trial. The FDA may also put the clinical trial on hold at any time after it commences if there are safety or effectiveness concerns with the drug or biological product being studied.

All clinical trials for new drugs and biologics must be conducted under the supervision of one or more qualified principal investigators in accordance with GCPs, which include the requirement that all research subjects provide their informed consent for their participation in any clinical trial. They must be conducted under protocols detailing, among other things, the objectives of the applicable phase of the trial, dosing procedures, research subject selection, exclusion criteria and the safety and effectiveness criteria to be evaluated. Each protocol must be submitted to the FDA as part of the IND application, and progress reports detailing the status of the clinical trials must be submitted to the FDA annually. Sponsors must also report to the FDA within specified timeframes, serious and unexpected adverse reactions, any clinically significant increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator’s brochure or any findings from other studies or animal or in vitro testing that suggest a significant risk in humans exposed to the vaccine candidate. An IRB at each institution participating in the clinical trial must review and approve the protocol before a clinical trial commences at that institution, approve the information regarding the trial and the consent form that must be provided to each research subject or the subject’s legal representative, and monitor the trial until completed.

Clinical trials are typically conducted in three sequential phases, but the phases may overlap, and different trials may be initiated with the same vaccine candidate within the same phase of development in similar or differing patient populations.

•Phase 1: Clinical trials may be conducted in a limited number of patients or healthy volunteers, as appropriate. The vaccine candidate is initially tested for safety and immunogenicity.

•Phase 2: The vaccine candidate is evaluated in a limited patient population to identify possible adverse effects and safety risks, to preliminarily evaluate the efficacy of the product for specific targeted diseases and to determine dosage tolerance, optimal dosage and dosing schedule.

•Phase 3: Clinical trials are undertaken to further evaluate dosage, clinical efficacy, potency and safety in an expanded patient population at geographically dispersed clinical trial sites. These clinical trials are intended to establish the overall risk/benefit ratio of the product and provide an adequate basis for product labeling.

In some cases, the FDA may require, or companies may voluntarily pursue, additional clinical trials after a product is approved to gain more information about the product. Completion of these so-called Phase 4 studies as post-marketing requirements may also be made a condition to approval of the BLA. These post-market clinical trials are used to gain additional experience from the treatment of patients in the intended therapeutic indication, particularly for long-term safety follow-up.

During all phases of clinical development, regulatory agencies require extensive monitoring and auditing of all clinical activities, clinical data and clinical trial investigators. Annual progress reports detailing the results of the clinical trials must be submitted to the FDA. Written IND application safety reports must be promptly submitted to the FDA and the investigators for serious and unexpected adverse events, any findings from other studies, tests in laboratory animals or in vitro testing that suggest a significant risk for human subjects or any clinically relevant increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator brochure. The sponsor must submit an IND application safety report within 15 calendar days after the sponsor determines that the information qualifies for reporting. The sponsor also must notify the FDA of any unexpected fatal or life-threatening suspected adverse reaction within seven calendar days after the sponsor’s initial receipt of the information. Phase 1, Phase 2 and Phase 3 clinical trials may not be completed successfully within any specified period, if at all. The FDA or the sponsor or its DSMB may place a clinical trial on hold at any time on various grounds, including a finding that the research subjects or patients are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the IRB’s requirements or if the biological product has been associated with unexpected serious harm to patients.

Assuming successful completion of all required testing in accordance with applicable regulatory requirements, the results of the preclinical studies and clinical trials, together with other detailed information, including information on the manufacture and composition of the vaccine candidate, are submitted to the FDA as part of a BLA requesting approval to market the vaccine candidate for a proposed indication or indications. The BLA must include all relevant data available from preclinical and clinical trials, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s CMC and proposed labeling, among other things. Under the Prescription Drug User Fee Act, the fees payable to the FDA for reviewing a BLA, as well as annual program user fees for approved products, can be substantial but are subject to certain limited deferrals, waivers and reductions that may be available. Additionally, no user fees are assessed on BLAs for products designated as orphan drugs, unless the product also includes a non-orphan indication. Each BLA submitted to the FDA for approval is reviewed for administrative completeness and reviewability within 60 days following receipt by the FDA of the application. If the BLA is found complete, the FDA will file the BLA, triggering a full review of the application. The FDA may refuse to file any BLA that it deems incomplete or not properly reviewable at the time of submission. The FDA’s established goal is to review 90% of priority BLAs within six months after the application is accepted for filing and 90% of standard BLAs within 10 months of the acceptance date, whereupon a review decision is to be made. Priority review will direct overall attention and resources to the evaluation of applications for products that, if approved, would be significant improvements in the safety or effectiveness of the treatment, diagnosis or prevention of serious conditions. In both standard and priority reviews, the review process is often significantly extended by FDA requests for additional information or clarification. The FDA reviews a BLA to determine, among other things, whether a product is safe, pure and potent and the facility in which it is manufactured, processed, packed or held meets cGMP standards designed to assure the product’s continued safety, purity and potency. The FDA may also convene an advisory committee to provide clinical insight on application review questions. The FDA is not bound by recommendations of an advisory committee, but it considers such recommendations when making decisions regarding approval.

Before approving a BLA, the FDA will typically inspect the facility or facilities where the product is manufactured. Some deficiencies found during the pre-approval inspection, if significant, could result in an FDA warning letter. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP and adequate to assure consistent production of the product within required specifications. Additionally, before approving a BLA, the FDA will typically inspect one or more clinical sites to assure compliance with GCP. If the FDA determines that the application, manufacturing process or manufacturing facilities are not acceptable, it will outline the deficiencies in the submission and often will request additional testing or information. Notwithstanding the submission of

any requested additional information, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval.

After the FDA evaluates a BLA and conducts inspections of manufacturing facilities where the investigational product and/or its drug substance will be produced, the FDA may issue an approval letter or a Complete Response Letter. An approval letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A Complete Response Letter will describe all of the deficiencies that the FDA has identified in the BLA, except that where the FDA determines that the data supporting the application are inadequate to support approval, the FDA may issue the Complete Response Letter without first conducting required inspections, testing submitted product lots and/or reviewing proposed labeling. In issuing the Complete Response Letter, the FDA may recommend actions that the applicant might take to place the BLA in condition for approval, including requests for additional information or clarification. The FDA may delay or refuse approval of a BLA if applicable regulatory criteria are not satisfied, require additional testing or information and/or require post-marketing testing and surveillance to monitor the safety or efficacy of a product.

If a product is approved, the FDA may impose limitations on the uses for which the product may be marketed, may require that warning statements or contraindications be included in the product labeling, may require that additional studies be conducted following approval as a condition of the approval and may impose restrictions and conditions on product distribution, prescribing or dispensing in the form of a Risk Evaluation and Mitigation Strategy (“REMS”), or otherwise limit the scope of any approval. A REMS is a safety strategy to manage a known or potential serious risk associated with a medicine and to enable patients to have continued access to such medicines by managing their safe use, and could include medication guides, physician communication plans or elements to assure safe use (also referred to as “ETASU”), such as restricted distribution methods, patient registries and other risk minimization tools. The FDA also may condition approval on, among other things, changes to proposed labeling or the development of adequate controls and specifications. In most cases, the FDA must approve a BLA supplement or a new BLA before a product may be marketed for other uses or before specific manufacturing or other changes may be made to the approved product. As a condition of approval, the FDA may also require one or more Phase 4 post-market studies and surveillance to further assess and monitor the product’s safety, purity, and potency after commercialization, and may limit further marketing of the product based on the results of these post-marketing studies. Also, product marketing may be restricted or product approvals may be withdrawn if compliance with regulatory standards is not maintained or if safety or manufacturing problems occur following initial marketing. In addition, new government requirements may be established that could delay or prevent regulatory approval of our vaccine candidates under development.

Both before and after the FDA approves a product, the manufacturer and the holder or holders of the BLA for the product are subject to comprehensive regulatory oversight. For example, quality control and manufacturing procedures must conform, on an ongoing basis, to cGMP requirements, and the FDA periodically inspects manufacturing facilities to assess compliance with cGMPs. Accordingly, manufacturers must continue to spend time, money and effort to maintain cGMP compliance.

Post-Approval Requirements

Any drug products manufactured or distributed by us or our partners pursuant to FDA approvals will be subject to pervasive and continuing regulation by the FDA, including, among other things, record-keeping requirements, reporting of adverse events, providing the FDA with updated safety and efficacy information, distribution requirements, complying with individual electronic records and signature requirements and complying with FDA promotion and advertising requirements. Once approval is granted, if compliance with regulatory standards is not maintained or if problems occur after the product reaches the market and the sponsor cannot remedy these deficiencies, the FDA may undertake a process to withdraw licensure. After approval, most changes to the approved product, such as adding new indications, specific manufacturing changes and additional labeling claims, are subject to further FDA review and approval. Biologic manufacturers, their subcontractors and other entities involved in the manufacture and distribution of approved drugs are required to register their establishments with the FDA and certain state agencies and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with cGMP regulations and other laws and regulations. Changes to the manufacturing process are strictly regulated and, depending on the significance of the change, may require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting requirements upon us and any third-party manufacturers that we may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMP and other aspects of regulatory compliance.

Discovery of previously unknown problems, including adverse events of unanticipated severity or frequency, or the failure to comply with the applicable regulatory requirements may result in restrictions on the marketing of a product or withdrawal of the product from the market as well as possible civil or criminal sanctions. Failure to comply with the applicable U.S. requirements at any time during the product development process, approval process or after approval, may

subject an applicant or manufacturer to administrative or judicial civil or criminal sanctions and adverse publicity. FDA sanctions could include refusal to approve pending applications, withdrawal or suspension of an approval or license, clinical holds, warning or untitled letters, product recalls, product seizures, safety alerts, Dear Healthcare Provider letters, total or partial suspension of production or distribution, injunctions, fines, refusals of government contracts, mandated corrective advertising or communications with doctors, debarment, restitution, disgorgement of profits, consent decrees or civil or criminal penalties.

The FDA strictly regulates labeling, advertising, promotion and other types of information on products that are placed on the market and imposes requirements and restrictions on drug manufacturers, such as those related to direct-to-consumer advertising, the prohibition on promoting products for uses or inpatient populations that are not described in the product’s approved labeling (known as “off-label use”), industry-sponsored scientific and educational activities and promotional activities involving the internet. Failure to comply with these requirements can result in, among other things, adverse publicity, untitled or warning letters, corrective advertising and potential civil and criminal penalties. Physicians may prescribe legally available products for uses that are not described in the product’s labeling and that differ from those tested by us and approved by the FDA. Such off-label uses are common across medical specialties. Physicians may believe that such off-label uses are the best treatment for many patients in varied circumstances. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, restrict the manufacturer’s communications on the subject of off-label use of their products.

Additional Controls for Biologics

To help reduce the increased risk of the introduction of adventitious agents, the PHS Act emphasizes the importance of manufacturing controls for products whose attributes cannot be precisely defined. The PHS Act also provides authority to the FDA to immediately suspend licenses in situations where there exists a danger to public health, to prepare or procure products in the event of shortages and critical public health needs, and to authorize the creation and enforcement of regulations to prevent the introduction or spread of communicable diseases in the United States and between states.

After a BLA is approved, the product will also be subject to official lot release as a condition of approval. As part of the manufacturing process, the manufacturer is required to perform specific tests on each lot of the product before it is released for distribution. If the product is subject to an official release by the FDA, the manufacturer submits samples of each lot of product to the FDA together with a release protocol showing a summary of the history of the manufacture of the lot and the results of all the manufacturer’s tests performed on the lot. The FDA may also perform specific confirmatory tests on lots of some products, such as vaccines, before releasing the lots for distribution by the manufacturer. In addition, the FDA conducts laboratory research related to the regulatory standards on the safety, purity, potency and effectiveness of biological products. As with drugs, after approval of biologics, manufacturers must address any safety issues that arise, are subject to recalls or a halt in manufacturing and are subject to periodic inspection after approval.

Expedited Development and Review Programs

A sponsor may seek approval of its vaccine candidate under programs designed to accelerate the FDA’s review and approval of new drugs and biological products that meet certain criteria. Specifically, new drugs and biological products are eligible for fast track designation if they are intended to treat a serious or life-threatening disease or condition and demonstrate the potential to address unmet medical needs for the disease or condition. For a fast track product, the FDA may consider sections of the BLA for review on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the application, the FDA agrees to accept sections of the application and determines that the schedule is acceptable and the sponsor pays any required user fees upon submission of the first section of the application. A fast track designated vaccine candidate may also qualify for priority review, under which the FDA sets the target date for FDA action on the BLA at six months after the FDA accepts the application for filing. Priority review is granted when there is evidence that the proposed product would be a significant improvement in the safety or effectiveness of the treatment, diagnosis or prevention of a serious disease or condition. If criteria are not met for priority review, the application is subject to the standard FDA review period of 10 months after the FDA accepts the application for filing. Priority review designation does not change the scientific/medical standard for approval or the quality of evidence necessary to support approval.

Under the accelerated approval program, the FDA may approve a BLA on the basis of either a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity or prevalence of the condition and the availability or lack of alternative treatments. Post-marketing studies or completion of ongoing studies after marketing approval are required to verify the biologic’s clinical benefit in relationship to the surrogate endpoint or ultimate outcome in relationship to the clinical

benefit. The Food and Drug Omnibus Reform Act and new FDA guidance, provide that confirmatory studies must be underway prior to approval of the BLA to gain approval under the accelerated approval pathway. In addition, the FDA currently requires as a condition for accelerated approval pre-approval of promotional materials, which could adversely impact the timing of the commercial launch of the product. The FDA may withdraw approval of a drug or indication approved under accelerated approval if, for example, the confirmatory trial fails to verify the predicted clinical benefit of the product.

In addition, a sponsor may seek FDA designation of its vaccine candidate as a breakthrough therapy if the vaccine candidate is intended to treat a serious or life-threatening disease or condition and preliminary clinical evidence indicates that the therapy may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. If the FDA designates a product as a breakthrough therapy, it may take actions appropriate to expedite the development and review of the application, which may include holding meetings with the sponsor and the review team throughout the development of the therapy; providing timely advice to, and interactive communication with, the sponsor regarding the development of the drug to ensure that the development program to gather the nonclinical and clinical data necessary for approval is as efficient as practicable; involving senior managers and experienced review staff, as appropriate, in a collaborative, cross-disciplinary review; assigning a cross-disciplinary project lead for the FDA review team to facilitate an efficient review of the development program and to serve as a scientific liaison between the review team and the sponsor; and considering alternative clinical trial designs when scientifically appropriate, which may result in smaller trials or more efficient trials that require less time to complete and may minimize the number of patients exposed to a potentially less efficacious treatment. A BTD comes with all of the benefits of fast track designation.

Even if a drug or biologic qualifies for one or more of these programs, the FDA may later decide that the drug no longer meets the conditions for qualification or that the time period for FDA review or approval will be shortened.

Biosimilars and Exclusivity

The ACA includes a subtitle called the Biologics Price Competition and Innovation Act of 2009 (“BPCIA”) which created section 351(k) of the PHS Act, establishing an abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-licensed reference biological product. The FDA has issued several guidance documents outlining an approach to review and approval of biosimilars. Biosimilarity, which requires that there be no clinically meaningful differences between the biological product and the reference product in terms of safety, purity and potency, can be shown through analytical studies, animal studies and a clinical trial or trials. Interchangeability requires that a product is biosimilar to the reference product and the product must demonstrate that it can be expected to produce the same clinical results as the reference product in any given patient and, for products that are administered multiple times to an individual, the biologic and the reference biologic may be alternated or switched after one has been previously administered without increasing safety risks or risks of diminished efficacy relative to exclusive use of the reference biologic.

Under the BPCIA, an application for a biosimilar product may not be submitted to the FDA until four years following the date that the reference product was first licensed by the FDA. In addition, the approval of a biosimilar product may not be made effective by the FDA until 12 years from the date on which the reference product was first licensed. During this 12-year period of exclusivity, another company may still market a competing version of the reference product if the FDA approves a full BLA for the competing product containing that applicant’s own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity and potency of its product. The FDA does not evaluate patent protection if another applicant submits a full BLA and not a biosimilar application, but the first license holder may choose to bring a patent infringement case, which may forestall marketing of such a competing product. The BPCIA also created certain exclusivity periods for biosimilars approved as interchangeable products. A biological product can also obtain pediatric market exclusivity in the United States. Pediatric exclusivity, if granted, adds six months to existing exclusivity periods and patent terms. This six-month exclusivity, which runs from the end of other exclusivity protection or patent term, may be granted based on the voluntary completion of a pediatric study in accordance with an FDA-issued “Written Request” for such a study.

United States Healthcare Reform

In the United States, there has been and continues to be, several legislative and regulatory changes and proposed changes regarding the healthcare system that could, among other things, prevent or delay marketing approval of vaccine candidates, restrict or regulate post-approval activities and affect the profitable sale of vaccine candidates.

Among policymakers and payors in the United States, there is significant interest in promoting changes in healthcare systems with the stated goals of containing healthcare costs, improving quality and/or expanding access. In the United States, the pharmaceutical industry has been a particular focus of these efforts and has been significantly affected by major

legislative initiatives. For example, in August 2022, the Inflation Reduction Act of 2022 (“IRA”) was signed into law, which among other things, enables the Centers for Medicare & Medicaid Services (“CMS”) to assert control over the prices of certain single-source drugs and biotherapeutics reimbursed under the Medicare Drug Price Negotiation Program, subjects drug manufacturers to potential civil monetary penalties and a significant excise tax for offering a price that is not equal to or less than the government-imposed “maximum fair price” under the law; imposes Medicare rebates for certain Part B and Part D drugs where relevant pricing metrics associated with the products increase faster than inflation; and redesigns the funding and benefit structure of the Medicare Part D program, potentially increasing manufacturer liability while capping annual out-of-pocket drug expenses for Medicare beneficiaries. These provisions started taking effect incrementally in late 2022 and currently are subject to various legal challenges. Further, as of January 1, 2023, the IRA eliminates patient cost sharing for FDA-approved adult vaccines that are recommended by the ACIP and covered under Medicare Part D and mandates that all state Medicaid programs cover FDA-approved adult vaccines that are recommended by the ACIP and their administration without cost sharing as of October 1, 2023. In addition, in December 2024, CMS released revised guidance on the Part D Manufacturer Discount Program, which requires manufacturers to take on more of the beneficiary cost previously subsidized by the federal government through the application of increased drug discounts. The IRA does not change either VFC or the related provisions added in 2010 under the ACA. VFC was established to give first-dollar coverage to children up to 18 years of age whose families could not pay for vaccinations while the ACA guaranteed coverage of vaccines without cost sharing for Americans who are either privately insured or newly covered in states that expanded Medicaid. Unless an exception applies, single-source vaccines can qualify for Medicare price negotiations 11 years after their BLA is approved and become subject to the IRA’s negotiated maximum fair price ceiling two years after that. In addition, certain vaccines, including pneumococcal virus vaccines, are excluded from the Medicare Part B inflation rebate. CMS also has stated in guidance and rulemaking that it is not imposing Medicare Part D inflation rebates at this time on vaccines and other drugs and biologics that are not “covered outpatient drugs” under Medicaid or otherwise do not have an obligation to report drug pricing data to Medicaid. Additionally, the IRA contains a limited small biotech exception, which applies on a drug-specific basis, and qualifying drugs may be exempt from possible pricing negotiation through 2028 and eligible for a lower limit (i.e., a price floor) on the potential maximum fair price in 2029 and 2030, if the manufacturers of those drugs continue to qualify each year. By February 1 of each year, CMS announces the list of the next Medicare Part B and Part D drugs selected for negotiation under the IRA.

Prior to the IRA, in March 2010, the ACA was passed, which substantially changed the way healthcare is financed by both the government and private insurers and significantly impacts the U.S. pharmaceutical industry. The ACA, among other things: (i) increased the minimum Medicaid rebates owed by manufacturers under the Medicaid Drug Rebate Program and extended the rebate program to individuals enrolled in Medicaid managed care organizations; (ii) created a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for certain drugs and biologics that are inhaled, infused, instilled, implanted or injected; (iii) established an annual, nondeductible fee on any entity that manufactures or imports certain specified branded prescription drugs and biologic agents apportioned among these entities according to their market share in specific government healthcare programs; (iv) expanded the eligibility criteria for Medicaid programs; (v) created a new Patient-Centered Outcomes Research Institute to oversee, identify priorities in, and conduct comparative clinical effectiveness research, along with funding for such research; (vi) created a new Medicare Part D coverage gap discount program which the IRA replaced, in which manufacturers were required to offer 70% point-of-sale discounts off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period, as a condition for the manufacturer’s outpatient drugs to be covered under Medicare Part D (as discussed above, the IRA replaced this program with the Part D Manufacturer Discount Program effective January 1, 2025); and (vii) established a Center for Medicare & Medicaid Innovation at the CMS to test innovative payment and service delivery models to lower Medicare and Medicaid spending, potentially including prescription drugs.

There have been judicial and legislative challenges to certain aspects of the ACA. By way of example, the Tax Cuts and Jobs Act of 2017 (the “Tax Act”) was signed into law and included a provision repealing, effective January 1, 2019, the tax-based shared responsibility payment imposed by the ACA on specific individuals who fail to maintain qualifying health coverage for all or part of a year that is commonly referred to as the “individual mandate.” The Bipartisan Budget Act of 2018, among other things, amended the ACA, effective January 1, 2019, to close the coverage gap in most Medicare drug plans, commonly referred to as the “donut hole.” On June 17, 2021, the U.S. Supreme Court dismissed a challenge on procedural grounds that argued the ACA is unconstitutional in its entirety because the "individual mandate" was repealed by Congress. More recently, a challenge to the ACA advanced to the U.S. Supreme Court. Specifically, in Braidwood Management v. Becerra, the plaintiffs argued that the ACA’s requirement that insurance cover certain preventive services without cost sharing is unconstitutional. In March 2023, the judge struck down the requirement with immediate nationwide effect by ruling, in part, that members of a panel charged under the ACA with recommending preventative services coverage had been appointed in an unconstitutional manner. Parties on both sides of the lawsuit appealed this ruling, and in June 2024 the U.S. Court of Appeals for the Fifth Circuit (Fifth Circuit) held, among other things, that the ACA’s requirement that group health plans and health insurance issuers cover certain preventative services without cost-sharing is unconstitutional. After granting the government’s petition for certiorari in the case, the U.S. Supreme Court announced its decision in June 2025 upholding the constitutionality of the ACA’s preventive‑services mandate.

Other legislative and executive changes have been proposed or adopted since the ACA was enacted. For example, on August 2, 2011, the Budget Control Act of 2011 was signed into law, which, among other things, resulted in aggregate reductions of Medicare payments to providers of 2% per fiscal year, which went into effect on April 1, 2013 and, due to subsequent legislative amendments to the statute, including the Infrastructure Investment and Jobs Act, will remain in effect through the first seven months of 2032, unless additional Congressional action is taken. On January 2, 2013, the American Taxpayer Relief Act of 2012 was signed into law, which, among other things, reduced Medicare payments to several providers, including hospitals, and increased the statute of limitations period for the government to recover overpayments to providers from three to five years.

At the state level, legislatures have increasingly passed legislation and implemented regulations designed to regulate pharmaceutical product pricing, including price or reimbursement constraints, discounts, restrictions on specific product access, marketing cost disclosure and transparency measures and, in some cases, measures designed to encourage importation from other countries and bulk purchasing.

On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was signed into law. The OBBBA is projected to decrease federal health care spending by approximately $1 trillion by reducing Medicaid spending and enrollment and making changes to federal Medicare spending. The law also made changes to ACA marketplace enrollment that are projected to decrease the number of individuals with marketplace coverage. It is unclear if these changes will impact the pharmaceutical industry.

United States Healthcare Fraud and Abuse Laws and Compliance Requirements

Federal and state healthcare laws and regulations restrict certain business practices in the biopharmaceutical industry, including anti-kickback and false claims laws and regulations, data privacy and security laws and regulations and transparency laws and regulations.

The federal Anti-Kickback Statute prohibits, among other things, individuals or entities from knowingly and willfully inducing or rewarding the referral of an individual, or offering, paying, soliciting or receiving remuneration, directly or indirectly, overtly or covertly, in cash or in-kind to induce or in return for purchasing, leasing, ordering or arranging for or recommending the purchase, lease or order of any item or service reimbursable under Medicare, Medicaid or other federal healthcare programs. The term “remuneration” has been broadly interpreted to include anything of value. A person or entity does not need to have actual knowledge of this statute or specific intent to violate it in order to have committed a violation.

Federal civil and criminal false claims laws, including the civil False Claims Act, which prohibits, among other things, any individual or entity from knowingly presenting, or causing to be presented, a false claim for payment of government funds or knowingly making, using or causing to be made or used a false record or statement material to an obligation to pay or transmit money to the federal government, or knowingly concealing or improperly avoiding or decreasing an obligation to pay money to the federal government. Private individuals, commonly known as “whistleblowers,” can bring civil False Claims Act qui tam actions, on behalf of the government and may share in amounts paid by the entity to the government in recovery or settlement. In addition, the government may assert that a claim including items or services resulting from a violation of the federal Anti-Kickback Statute constitutes a false or fraudulent claim for purposes of the civil False Claims Act.

The federal Health Insurance Portability and Accountability Act of 1996 (“HIPAA”) created additional federal civil and criminal statutes that prohibit, among other things, knowingly and willfully executing a scheme to defraud any healthcare benefit program, including private third-party payors, or making any false, fictitious or fraudulent statement in connection with the delivery of or payment for healthcare benefits, items or services, including those by private payors. Similar to the federal Anti-Kickback Statute, a person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation.

In addition, HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act, and their implementing regulations, imposes specific requirements relating to the privacy, security and transmission of protected health information on HIPAA covered entities, which include certain healthcare providers, health plans and healthcare clearinghouses and their business associates and covered subcontractors who conduct certain activities for or on their behalf involving protected health information on their behalf.

The federal Physician Payments Sunshine Act requires certain manufacturers of drugs, devices, biologics and medical supplies for which payment is available under Medicare, Medicaid or the Children’s Health Insurance Program, with specific exceptions, to report annually to CMS information related to payments or other transfers of value made to physicians (defined to include doctors, dentists, optometrists, podiatrists and chiropractors), other healthcare professionals

(such as physician assistants and nurse practitioners) and teaching hospitals, and applicable manufacturers and applicable group purchasing organizations to report annually to CMS ownership and investment interests held by physicians and their immediate family members.

Similar state, local and foreign healthcare laws and regulations, such as state anti-kickback and false claims laws, may be broader in scope and may apply regardless of payor, in addition to items and services reimbursed under Medicaid and other state programs. Additionally, there are state laws that require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government, or otherwise restrict payments that may be made to healthcare providers and other potential referral sources; state laws and regulations that require drug manufacturers to file reports relating to pricing and marketing information or which require tracking gifts and other remuneration and items of value provided to physicians, other healthcare providers and entities; state and local laws that require the registration of pharmaceutical sales representatives; and state and local laws governing the privacy and security of health information in some circumstances, many of which differ from each other in significant ways and often are not preempted by HIPAA, thus complicating compliance efforts.

Efforts to ensure compliance with applicable healthcare laws and regulations can involve substantial costs. Violations of federal and state healthcare laws described above can result in significant penalties, including, without limitation, the imposition of significant civil, criminal and administrative penalties, damages, monetary fines, disgorgement, individual imprisonment, exclusion from participation in Medicare, Medicaid and other U.S. healthcare programs, integrity oversight and reporting obligations, contractual damages, reputational harm, diminished profits and future earnings and curtailment or restructuring of operations.

Foreign Regulation

In addition to regulations in the United States, we expect to be subject to a variety of foreign regulations governing clinical trials and commercial sales and distribution of our vaccine candidates. Whether or not we obtain FDA approval for a vaccine candidate, we must obtain approval from the comparable regulatory authorities of foreign countries or economic areas, such as the European Union, before we may commence clinical trials or market products in those countries or areas. The approval process and requirements governing the conduct of clinical trials, product licensing, pricing and reimbursement vary greatly from place to place, and the time may be longer or shorter than that required for FDA approval.

Certain countries outside of the United States have a process that requires the submission of a clinical trial application, much like an IND prior to the commencement of human clinical trials. In Europe, for example, a clinical trial application (“CTA”) must be submitted to the competent national health authority and to independent ethics committees in each country in which a company intends to conduct clinical trials. Once the CTA is approved in accordance with a country’s requirements, clinical trial development may proceed in that country. In all cases, the clinical trials must be conducted in accordance with GCPs and other applicable regulatory requirements.

The requirements and process governing the conduct of clinical trials, product licensing, pricing and reimbursement vary from country to country. In all cases, the clinical trials are conducted in accordance with GCP and the applicable regulatory requirements and the ethical principles that have their origin in the Declaration of Helsinki.

Under European Union regulatory systems, a company may submit marketing authorization applications either under a centralized or decentralized procedure. The centralized procedure is compulsory for medicinal products produced by biotechnology or those medicinal products containing new active substances for specific indications such as the treatment of AIDS, cancer, neurodegenerative disorders, diabetes, viral diseases and designated orphan medicines, and optional for other medicines which are highly innovative. Under the centralized procedure, a marketing application is submitted to the European Medicines Agency (“EMA”) where it will be evaluated by the Committee for Medicinal Products for Human Use, and a favorable opinion typically results in the grant by the European Commission of a single marketing authorization that is valid for all European Union member states within 67 days of receipt of the opinion. The initial marketing authorization is valid for five years, but once renewed is usually valid for an unlimited period.

To market a medicinal product in the European Economic Area (“EEA”), which is comprised of the 28 Member States of the EU plus Norway, Iceland and Liechtenstein, we must obtain a Marketing Authorization, (“MA”). There are two types of marketing authorizations:

•The Community MA, which is issued by the European Commission through the Centralized Procedure, based on the opinion of the Committee for Medicinal Products for Human Use of the EMA, and which is valid throughout the entire territory of the EEA. The Centralized Procedure is mandatory for certain types of products, such as biotechnology medicinal products, orphan medicinal products, advanced therapy products and medicinal products

containing a new active substance indicated for the treatment certain diseases, such as AIDS, cancer, neurodegenerative disorders, diabetes, auto-immune and viral diseases. The Centralized Procedure is optional for products containing a new active substance not yet authorized in the EEA, or for products that constitute a significant therapeutic, scientific or technical innovation or which are in the interest of public health in the EU; and

•National MAs, which are issued by the competent authorities of the Member States of the EEA and only cover their respective territory, are available for products not falling within the mandatory scope of the Centralized Procedure. Where a product has already been authorized for marketing in a Member State of the EEA, this National MA can be recognized in another Member State through the Mutual Recognition Procedure. If the product has not received a National MA in any Member State at the time of application, it can be approved simultaneously in the various Member States through the Decentralized Procedure.

Under the above-described procedures, before granting the MA, the EMA, or the competent authorities of the Member States of the EEA make an assessment of the risk-benefit balance of the product on the basis of scientific criteria concerning its quality, safety and efficacy.

If we fail to comply with applicable foreign regulatory requirements, we may be subject to, among other things, fines, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution.

Additional Regulation

We are also subject to regulation under the Occupational Safety and Health Act, the Environmental Protection Act, the Toxic Substances Control Act, the Resource Conservation and Recovery Act and other present and potential federal, state or local regulations. These and other laws govern our use, handling and disposal of various biological and chemical substances used in, and waste generated by our operations. Our research and development involve the controlled use of hazardous materials, chemicals, bacteria and viruses. Although we believe that our safety procedures for handling and disposing of such materials comply with the standards prescribed by state and federal regulations, the risk of accidental contamination or injury from these materials cannot be completely eliminated. In the event of such an accident, we could be held liable for any damages that result and any such liability could exceed our resources.

There have been a number of federal and state proposals during the last few years regarding the pricing of pharmaceutical and biological products, government control and other changes to the healthcare system of the United States. It is uncertain what legislative proposals will be adopted or what actions federal, state or private payors for medical goods and services may take in response to any healthcare reform proposals or legislation. We cannot predict the effect medical or healthcare reforms may have on our business, and no assurance can be given that any such reforms will not have a material adverse effect.

Privacy and Data Protection Laws

We are or may become subject to numerous data privacy and security obligations, including federal, state, local, and foreign laws, regulations, guidance, and industry standards related to data privacy, security, and the protection of health-related and other personal data. Such obligations may include, without limitation, the Federal Trade Commission Act, the California Consumer Privacy Act of 2018, as amended by the California Privacy Rights Act of 2020 (the “CPRA” and collectively, the “CCPA”), the European Union’s General Data Protection Regulation 2016/679 (the “EU GDPR”), and the EU GDPR as it forms part of the United Kingdom (the “UK”) law by virtue of section 3 of the European Union (Withdrawal) Act 2018, or the UK GDPR, and the ePrivacy Directive. In addition, numerous U.S. states — including, but not limited to California, Colorado, Connecticut, Montana, Oregon, Utah, Texas, and Virginia — have enacted comprehensive data privacy laws in the past few years, and other U.S. states, including Washington and Nevada, have enacted consumer health data privacy laws. Certain privacy and data protection laws and regulations, including HIPAA, establish standards for the protection of certain health information and impose requirements relating to the use, disclosure, and safeguarding of individually identifiable health information by covered entities and their business associates.

Foreign data privacy and security laws (including, but not limited to, the EU GDPR and UK GDPR) may impose significant and complex compliance obligations on entities that are subject to those laws. As one example, the EU GDPR applies to any company established in the EEA, and to companies established outside the EEA that process personal data in connection with the offering of goods or services to data subjects in the EEA or the monitoring of the behavior of data subjects in the EEA. Failure to comply with the requirements of the EU GDPR and the applicable national data protection laws of the EU member states may result in: temporary or definite bans on processing of personal data and other corrective actions; fines of up to €20,000,000 or up to 4% of the total worldwide annual turnover of the preceding financial year,

whichever is higher, and other administrative penalties; or private litigation related to processing of personal data brought by classes of data subjects or consumer protection organizations authorized at law to represent their interests.

See the section titled “Risks Related to Government Regulation” for additional information about the laws and regulations to which we are or may become subject to and about the risks to our business associated with such laws and regulations.

Employees & Human Capital

As of December 31, 2025, we had 507 full-time employees, with most of those based in the United States. Of our full-time employees, approximately 16% have Ph.D. or M.D. degrees. None of our employees are represented by labor unions or covered by collective bargaining agreements. We consider our relationship with our employees to be good.

We recognize that attracting, incentivizing, retaining and promoting talented employees is vital to our success. We aim to create a supportive and empowering environment in which our employees can grow, succeed and advance their careers, with the overall goal of developing, expanding and retaining a world-class workforce aligned with our current pipeline and future business goals. Our efforts to recruit and retain a high-performing and committed workforce include providing competitive compensation and benefits, including equity incentive compensation, and supporting our employees’ well-being and success.

Continuous development is essential to achieving our organization’s goals. We are committed to offering both in-person and virtual training opportunities, as well as hands-on learning experiences through cross-functional exposure, such as presentations and job shadowing. In addition, we value our employees’ insights and provide virtual and onsite forums where our employees can provide feedback, recognize each other’s contributions and accomplishments, and offer suggestions for enhancing our work environment.

Corporate and Other Information

We are headquartered in San Carlos, California. We were incorporated in the state of Delaware on November 27, 2013 as SutroVax, Inc. and we changed our name to Vaxcyte, Inc. in May 2020. Our website is located at https://www.vaxcyte.com. Our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K including their exhibits, proxy and information statements, and amendments to those reports filed or furnished pursuant to Section 13(a), 14, and 15(d) of the Securities Exchange Act of 1934 (as amended, the “Exchange Act”) are available through the “Investors & Media” portion of our website free of charge as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. Information on our website is not part of this Annual Report on Form 10-K or any of our other securities filings unless specifically incorporated herein or therein by reference. In addition, our filings with the SEC may be accessed through the SEC’s website at http://www.sec.gov. All statements made in any of our securities filings, including all forward-looking statements or information, are made as of the date of the document in which the statement is included, and we do not assume or undertake any obligation to update any of those statements or documents unless we are required to do so by law.