The bivalent vaccine maintained consistently high protective efficacy for both RSV A and RSV B disease through two seasons after a single dose.

Pfizer’s Abrysvo vaccine for respiratory syncytial virus (RSV) provided high protective efficacy for RSV A and RSV B through two seasons after a single dose in older adults, according to top-line results from the ongoing pivotal phase 3 RENOIR clinical trial. 

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,” says Annaliesa Anderson, PhD, senior vice president and chief scientific officer, vaccine research and development, at Pfizer, in a 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.”

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.

In May 2023, the US Food and Drug Administration (FDA) approved Abrysvo for the prevention of LRTD caused by RSV in individuals 60 years of age or older. In August 2023, the FDA approved the vaccine for the prevention of LRTD and severe LRTD caused by RSV in infants from birth up to 6 months of age by active immunization of pregnant individuals at 32 through 36 weeks gestational age.

This was followed in September 2023 with the Advisory Committee on Immunization Practices’ 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.

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