Investigational vaccine shows strong immune responses in infants equivalent to PREVNAR 20^® on shared serotypes and for five new serotypes, potentially offering the broadest protection against invasive pneumococcal disease (IPD) for pediatric population in the U.S.

Company Website: https://www.pfizer.com
NEW YORK -- (Business Wire)

Pfizer Inc. (NYSE: PFE) today announced detailed results across serotypes from a Phase 2 study (NCT06524414) for its investigational 25-valent pneumococcal conjugate vaccine candidate, PF-07872412 (25vPnC), in infants. In the study, a four-dose series of 25vPnC elicited robust immune responses against all 25 serotypes and showed safety and tolerability comparable to four doses of PREVNAR 20^® (Pneumococcal 20-valent Conjugate Vaccine). These findings were shared today in an oral presentation at IDWeek 2026 in Washington, D.C.¹

These data support the ongoing Phase 3 development program for 25vPnC, which, if successful, could help provide protection against serotypes collectively responsible for approximately 84% of invasive pneumococcal disease (IPD) cases among children under five years of age in the U.S.²

“These encouraging data build on more than 25 years of progress in protecting children from serious pneumococcal disease with PREVNAR vaccines. By expanding serotype coverage and applying next-generation technology to the historically challenging serotype 3, this candidate aims to extend the substantial reductions in disease that existing vaccines have achieved. If successful, it could help provide children with the broadest protection against invasive pneumococcal disease to date.”

— Annaliesa Anderson, Ph.D., Senior Vice President and Chief Vaccines Officer, Pfizer

Phase 2 Study Results Across 25 Serotypes

The Phase 2 study is evaluating the safety, tolerability, and immunogenicity of the 25-valent vaccine candidate(25vPnC) compared with PREVNAR 20 in healthy infants. These data build on results announced earlier this year showing:

• Robust immune responses against all 25 serotypes one month after Dose 3 and one month after Dose 4, including against all five new serotypes (15A, 23A, 23B, 24F, and 35B).^{Rates of local reactions, systemic events, and adverse events were balanced across the 25-valent vaccine candidate and PREVNAR 20 groups in the Phase 2 trial. Adverse events were consistent with conditions commonly diagnosed in this age group. There were no related serious adverse events identified in the study. 1}
• The 25-valent vaccine candidate elicited an enhanced immune response against serotype 3 compared with PREVNAR 20, generating GMCs that were 8.8-fold higher one month after Dose 3 and approximately 15-fold higher one month after Dose 4. ¹ It utilizes next-generation technology specifically designed to elicit a more robust immune response against serotype 3, which accounts for 10.6% of all IPD in children under five years old in the U.S. ²
• 25-valent vaccine candidate also elicited functional responses in the opsonophagocytic activity assay (OPA) one month after Dose 4 for all 25 target serotypes, demonstrating booster effects. ¹ This result demonstrates the vaccine candidate’s potential to generate antibodies that can contribute to the functional killing of pneumococcal bacteria.³

Detailed results from the presentation can be found online here.

Continuing Pfizer’s Commitment to Pneumococcal Disease Prevention

These results build on Pfizer’s long-standing commitment to protecting people from pneumococcal disease. Pfizer is advancing two next-generation pneumococcal conjugate vaccine candidates across pediatric and adult populations.

• In children, 25vPnC is being evaluated in three Phase 3 studies that began earlier in 2026, with up to 6,830 participants randomized to receive 25vPnC or PREVNAR 20.^4,5,6 Additionally, Pfizer has completed enrollment of a Phase 3 study to demonstrate the consistency of three manufacturing lots of 25vPnC.⁷
• The five new serotypes (15A, 23A, 23B, 24F, and 35B) are estimated to account for an additional ~30% of pediatric invasive pneumococcal disease cases in the U.S. compared with PREVNAR 20.² It also uses next-generation technology designed to improve responses to serotype 3, which accounts for 10.6% of invasive pneumococcal disease in U.S. children under five years of age.^1,2
• In adults, Pfizer plans to bring a fifth-generation, 35-valent vaccine candidate into clinical development by the end of 2026, pending alignment from regulatory authorities.

For more information on Pfizer’s Commitment to Vaccines, please visit: Vaccines | Pfizer | Pfizer. More information on Pfizer’s overall presence at IDWeek 2026 is here.

U.S. INDICATION AND IMPORTANT SAFETY INFORMATION FOR PREVNAR 20

INDICATION

PREVNAR 20 is a vaccine approved for:

• the prevention of invasive disease caused by 20 Streptococcus pneumoniae strains (1, 3, 4, 5, 6A, 6B, 7F, 8, 9V, 10A, 11A, 12F, 14, 15B, 18C, 19A, 19F, 22F, 23F, and 33F) in individuals 6 weeks of age and older.
• the prevention of otitis media (middle ear infection) caused by 7 of the 20 strains in individuals 6 weeks through 5 years.
• active immunization for the prevention of pneumonia caused by Streptococcus pneumoniae strains 1, 3, 4, 5, 6A, 6B, 7F, 8, 9V, 10A, 11A, 12F, 14, 15B, 18C, 19A, 19F, 22F, 23F, and 33F in individuals 18 years of age and older.

The indication for the prevention of pneumonia caused by S. pneumoniae serotypes 8, 10A, 11A, 12F, 15B, 22F, and 33F in individuals 18 years of age and older is approved based on immune responses. Continued approval may depend on a supportive study.

IMPORTANT SAFETY INFORMATION

• PREVNAR 20 should not be given to anyone who has had a severe allergic reaction to any component of Prevnar 20 or to diphtheria toxoid.
• Individuals with weakened immune systems may have a lower immune response. Safety data are not available for these groups.
• A temporary pause in breathing after getting a vaccine has been observed in some infants who were born prematurely. For premature infants, talk to your healthcare provider about the infant's medical status when deciding to get vaccinated with Prevnar 20.
• In individuals 2, 4, 6, and 12 through 15 months of age vaccinated with a 4-dose schedule, the most common side effects reported at a rate of >10% were irritability, pain at the injection site, drowsiness, decreased appetite, injection site redness, injection site swelling, and fever.
• In individuals 15 months through 17 years of age vaccinated with a single dose, the most common side effects reported at a rate of >10% were irritability, pain at the injection site, drowsiness, fatigue, muscle pain, decreased appetite, injection site swelling, injection site redness, headache, and fever.
• In individuals 18 years and older, the most common side effects reported at a rate of >10% were pain at the injection site, muscle pain, fatigue, headache, and joint pain. Also, injection site swelling was common in individuals 18 years through 59 years of age.
• Ask your healthcare provider about the risks and benefits of Prevnar 20. Only a healthcare provider can decide if PREVNAR 20 is right for you or your child.

Please click for PREVNAR 20 Full Prescribing Information.

About Pfizer: Breakthroughs That Change Patients’ Lives

At Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products, including innovative medicines and vaccines. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world's premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For more than 175 years, we have worked to make a difference for all who rely on us. We routinely post information that may be important to investors on our websiteatwww.Pfizer.com. In addition, to learn more, please visit us on www.Pfizer.com and follow us on X at @Pfizer and @Pfizer_News, LinkedIn, YouTube and like us on Facebook at www.facebook.com/Pfizer/.

Disclosure Notice

The information contained in this release is as of October 24, 2026. Pfizer assumes no obligation to update forward-looking statements contained in this release as the result of new information or future events or developments.

This release contains forward-looking information about an investigational pediatric 25-valent pneumococcal conjugate vaccine candidate PF-07872412 (25vPnC) and an investigational adult fifth-generation, 35-valent vaccine candidate vaccine candidate (35vPnC), including their potential benefits, results from a Phase 2 study of 25vPvC in infants and clinical development plans and timing for 25vPnC and 35vPnC, that involves substantial risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such statements. Risks and uncertainties include, among other things, the uncertainties inherent in research and development, including the ability to meet anticipated clinical endpoints, commencement and/or completion dates for our clinical trials, regulatory submission dates, regulatory approval dates and/or launch dates, as well as the possibility of unfavorable new clinical data and further analyses of existing clinical data; risks associated with initial, preliminary or interim data; the risk that clinical trial data are subject to differing interpretations and assessments by regulatory authorities; whether regulatory authorities will be satisfied with the design of and results from our clinical studies; whether and when applications may be filed in any jurisdictions for 25vPnC or 35vPnC; whether and when any such applications may be approved by regulatory authorities, which will depend on myriad factors, including making a determination as to whether the product’s benefits outweigh its known risks and determination of the product’s efficacy and, if approved, whether 25vPnC and 35vPnC will be commercially successful; decisions by regulatory authorities impacting labeling, manufacturing processes, safety and/or other matters that could affect the availability or commercial potential of 25vPnC and 35vPnC; uncertainties regarding the ability to obtain or maintain recommendations from vaccine advisory or technical committees and other public health authorities and uncertainties regarding the commercial impact of any such recommendations; risks and uncertainties related to changes to vaccine or other healthcare policy in the U.S.; challenges related to public vaccine confidence or awareness; risks and uncertainties related to issued or future executive orders or other new, or changes in, laws or regulations; uncertainties regarding the impact of COVID-19 on Pfizer’s business, operations and financial results; and competitive developments.

A further description of risks and uncertainties can be found in Pfizer’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025 and in its subsequent reports on Form 10-Q, including in the sections thereof captioned “Risk Factors” and “Forward-Looking Information and Factors That May Affect Future Results”, as well as in its subsequent reports on Form 8-K, all of which are filed with the U.S. Securities and Exchange Commission and available at www.sec.gov and www.pfizer.com.

References

1. Smith M, Flint L, Trammel J, et al. Immunogenicity of a 25-Valent Pneumococcal Coverage Vaccine Compared with PCV20 in Healthy Infants: Evaluating A Candidate to Improve Pneumococcal Coverage in a Phase 2 Trial. Presented at IDWeek 2026; October 24, 2026; Washington DC.
2. Centers for Disease Control and Prevention. Surveillance Reports, 2020-2024. Active Bacterial Core surveillance (ABCs). Accessed October 12, 2026. https://www.cdc.gov/abcs/reports/index.html
3. Paschall AV, Middleton DR, Avci FY. Opsonophagocytic Killing Assay to Assess Immunological Responses Against Bacterial Pathogens. J Vis Exp. 2019;(146):10.3791/59400.
4. ClinicalTrials.gov. A Study to Learn About How a New Pneumococcal Vaccine Works in Infants. Updated September 8, 2026. Accessed October 12, 2026. https://clinicaltrials.gov/study/NCT07629440
5. ClinicalTrials.gov. A Study to Learn About the Safety of an Expanded Pneumococcal Vaccine in Healthy Infants. Updated September 15, 2026. Accessed October 12, 2026. https://clinicaltrials.gov/study/NCT07573462
6. ClinicalTrials.gov. Study to Learn About Safety, Tolerability, and Immune Response of a Catch-up Pneumococcal Vaccine in Children and Adolescents (NCT07660198). Updated August 31, 2026. Accessed October 12, 2026. https://clinicaltrials.gov/study/NCT07660198
7. ClinicalTrials.gov. A Study to Assess the Safety, Tolerability, and Immunogenicity of 3 Lots of a Multivalent Pneumococcal Conjugate Vaccine Administered to Adults. Updated September 23, 2026. Accessed October 12, 2026. https://clinicaltrials.gov/study/NCT07794748

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Source: Pfizer Inc.