PfizerPfizer Inc. (NYSE: PFE) today announced top-line ABRYSVO® vaccine efficacy and safety data for respiratory syncytial virus (RSV) in adults 60 years of age and older following a second season in the Northern and Southern Hemispheres from the ongoing pivotal Phase 3 clinical trial (NCT05035212) RENOIR (RSV vaccine Efficacy study iNOlder adults Immunized against RSV disease). Vaccine efficacy against RSV-associated lower respiratory tract disease (LRTD), defined by three or more symptoms, after disease surveillance in season two was 77.8% (95.0% CI: 51.4, 91.1); vaccine efficacy following season one was 88.9% (95.0% CI: 53.6%, 98.7%)(1), which demonstrates durable efficacy after two seasons.

Consistent vaccine efficacy was demonstrated for both RSV A and RSV B after season two with vaccine efficacy against each subtype of ≥80% for LRTD with three or more symptoms. Vaccine efficacy was also sustained against less severe LRTD, defined by two or more symptoms, from 65.1% (95.0%% CI: 35.9%, 82.0%)1 after season one to 55.7% (95.0% CI: 34.7%, 70.4%) after the end of season two. Vaccine efficacy against RSV-associated LRTD, defined by three or more symptoms, across both seasons after approximately 16.4 months of disease surveillance was 81.5% (95.0% CI: 63.3, 91.6).

No new adverse events were reported through the second RSV season beyond what was reported by subjects in the clinical trial during the first season. Pfizer is conducting post-marketing studies and surveillance programs to inform the safety profile of ABRYSVO.

"We are encouraged by the level of protection that we observed after two full RSV seasons for ABRYSVO," said Annaliesa Anderson, Ph.D., Senior Vice President and Chief Scientific Officer, Vaccine Research and Development, Pfizer. "This new data indicate that broad and durable protection against both types of RSV that cause disease, RSV A and RSV B, is the potential benefit to having a bivalent vaccine."

Pfizer intends to submit these data to regulatory authorities and vaccine technical committees. The company also intends to publish these findings in a peer-reviewed scientific journal and share them at an upcoming scientific congress.

About RSV

RSV is a contagious virus and a common cause of respiratory illness.(2) The virus can affect the lungs and breathing passages of an infected individual and can potentially cause severe illness in young infants, older adults, and individuals with certain chronic medical conditions.(3,4,5) In the United States alone, among older adults, RSV infections account for approximately 60,000-160,000 hospitalizations and 6,000-13,000 deaths each year.(6,7,8,9,10,11,12,13,14) RSV disease is caused by the respiratory syncytial virus. There are two major subgroups of RSV: RSV A and RSV B. Both subgroups cause disease and can co-circulate or alternate predominance from season to season.


Pfizer currently is the only company with an RSV vaccine to help protect older adults, as well as infants through maternal immunization. ABRYSVO is a bivalent vaccine that was designed to provide broad protection against all RSV-LRTD, regardless of the virus subgroup. The RSV fusion protein (F) in the prefusion conformation is a major target of virus infection blocking antibodies and is the basis of Pfizer’s RSV vaccine. Sequence variability in F between RSV subgroup A and B strains clusters in potent neutralizing antibody binding sites on prefusion F.

In May 2023, the FDA approved ABRYSVO for the prevention of LRTD caused by RSV in individuals 60 years of age or older. ABRYSVO is a bivalent vaccine that was designed to provide broad protection regardless whether strain. This was followed by the ACIP's recommendation of the vaccine for use in adults 60 years of age and older with shared clinical decision making, which occurred in June 2023. In August 2023, the FDA approved ABRYSVO for the prevention of LRTD and severe LRTD caused by RSV in infants from birth up to six months of age by active immunization of pregnant individuals at 32 through 36 weeks gestational age. This was followed in September 2023 with ACIP’s recommendation for maternal immunization to help protect newborns from RSV seasonally where the vaccine should be administered from September through January in most of the continental United States.

Also in August 2023, Pfizer announced that the European Medicines Agency (EMA) granted marketing authorization for ABRYSVO for both older adults and maternal immunization to help protect infants. The vaccine has also received approvals from la Administración Nacional de Medicamentos, Alimentos y Tecnología Médica (ANMAT) of Argentina in September 2023; the Medicines and Healthcare products Regulatory Agency (MHRA) of the United Kingdom in November 2023; Health Canada of Canada in January 2024; the Pharmaceutical Administration Bureau of Macau in February 2024; and for maternal immunization to help protect infants by the Ministry of Health, Labour, and Welfare of Japan in January 2024.

Pfizer has also initiated two additional clinical trials evaluating ABRYSVO. One trial is being conducted in children ages two to less than 18 years who are at higher risk for RSV disease.(15) A second trial is evaluating adults ages 18 to 59 years at higher risk for RSV due to underlying medical conditions such as asthma, diabetes and chronic obstructive pulmonary disease (COPD), and adults ages 18 and older who are immunocompromised and at high risk for RSV.

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 170 years, we have worked to make a difference for all who rely on us.

1. Walsh EE, Gonzalo PM, et al. “Efficacy and Safety of a Bivalent RSV Prefusion F Vaccine in Older Adults.” The New England Journal of Medicine. April 20, 2023.
2. Centers for Disease Control and Prevention. Respiratory Syncytial Virus Infection (RSV). Updated December 18, 2020.
3. Centers for Disease Control and Prevention. RSV Transmission. Updated December 18, 2020.
4. Centers for Disease Control and Prevention. Respiratory Syncytial Virus Infection (RSV) - Older Adults are at High Risk for Severe RSV Infection Fact Sheet.
5. Centers for Disease Control and Prevention. RSV in Infants and Young Children.
6. Centers for Disease Control and Prevention. RSV Surveillance & Research.
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11. Centers for Disease Control and Prevention. October 2022 ACIP Meeting Slides. ACIP Adult RSV Work Group Considerations. Available at:
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13. Matias G, Taylor R, Haguinet F, et al. Estimates of Mortality Attributable to Influenza and RSV in the United States during 1997–2009 by Influenza Type or Subtype, Age, Cause of Death, and Risk Status. Influenza Other Respir Viruses. 2014; 8(5):507-15.
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15. Pfizer Second-Quarter 2023 Earnings Teleconference Presentation, August 1, 2023, page, 24,