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Pfizer’s Bivalent Respiratory Syncytial Virus Vaccine Shows Promising Efficacy Across Two Seasons


Abrysvo was found to produce durable efficacy against respiratory syncytial virus across two seasons in adults 60 years of age and older.

Image credit: jarun011 | stock.adobe.com. Blood sample positive with respiratory syncytial virus (RSV)

Image credit: jarun011 | stock.adobe.com

Top-line data from the ongoing, pivotal Phase III RENOIR clinical trial (NCT05035212) demonstrated that Pfizer’s bivalent respiratory syncytial virus (RSV) prefusion F (RSVpreF) vaccine Abrysvo produces durable efficacy against respiratory syncytial virus (RSV) across two seasons in adults 60 years of age and older. Efficacy against RSV-associated lower respiratory tract disease (LRTD), defined as three or more symptoms, was 88.9% after the first season, whereas efficacy was 77.8% after the second season.1

“We are encouraged by the level of protection that we observed after two full RSV seasons for Abrysvo,” Annaliesa Anderson, PhD, Pfizer senior vice president and chief scientific officer, Vaccine Research and Development, said in a press release. “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.”1

RSV develops in 3% to 7% of healthy older adults in the United States and Europe annually, with an estimated 177,000 hospitalizations and 14,000 deaths each year in the United States alone. RSV can be especially severe in older adults, as approximately 18% of hospitalizations involve admission to an intensive care unit; 31% of individuals receive home health services at discharge; and 26% die within one year post admission. Among older adults, RSV is a common cause of LRTD, which affects the lungs and can cause life-threatening pneumonia and bronchiolitis. The CDC has found that RSV leads to approximately 60,000-120,000 annual hospitalizations and 6,000-10,000 annual deaths among adults 65 years of age and older.2

Abrysvo was approved by the FDA in June 2023 to prevent LRTD caused by RSV in individuals 60 years of age and older.3 Abrysvo is based on foundational basic science discoveries, such as findings from the National Institutes of Health (NIH), detailing the crystal structure of prefusion F, a vital form of the viral fusion protein (F) used by RSV to attack human cells. NIH research indicates that antibodies specific to the prefusion form had high efficacy preventing viral infection, which indicates that a prefusion F-based vaccine may provide optimal protection against RSV, according to Pfizer.3

Findings from the RENOIR trial showed consistent vaccine efficacy across both RSV A and RSV B after two seasons, producing vaccine efficacy against each subtype of ≥80% for LRTD with three or more symptoms. Efficacy against less severe LRTD, defined as two or more symptoms, was 65.1% after the first season and dropped to 55.7% after the second season. Efficacy against RSV-associated LRTD, defined as three or more symptoms, after approximately 16.4 months of surveillance was 81.5%.

There were no new adverse events observed following the second RSV season that differed from what was reported during the first season. Pfizer is currently conducting post-marketing studies and surveillance programs to continue monitoring the safety profile of Abrysvo. Pfizer announced plans to submit the study data to regulatory authorities and vaccine technical committees, in addition to publishing the findings in a peer-reviewed journal and sharing the data at an upcoming scientific meeting.


1. Pfizer Announces Positive Top-Line Data for Full Season Two Efficacy of ABRYSVO® for RSV in Older Adults. Pfizer. News release. February 29, 2024. Accessed February 29, 2024. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-positive-top-line-data-full-season-two

2. FDA Approves First Respiratory Syncytial Virus (RSV) Vaccine. FDA. News release. May 3, 2023. Accessed February 29, 2024. https://www.fda.gov/news-events/press-announcements/fda-approves-first-respiratory-syncytial-virus-rsv-vaccine?utm_medium=email&utm_source=govdelivery.

3. U.S. FDA Approves ABRYSVO™, Pfizer’s Vaccine for the Prevention of Respiratory Syncytial Virus (RSV) in Older Adults. Pfizer. News release. May 31, 2023. Accessed February 29, 2024. https://www.pfizer.com/news/press-release/press-release-detail/us-fda-approves-abrysvotm-pfizers-vaccine-prevention

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