Abrysvo Efficacy Sustained in Older Adults Through Second RSV Season

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Abrysvo, the bivalent respiratory syncytial virus (RSV) vaccine from Pfizer, was found nearly 78% effective in a second full RSV season in preventing RSV-associated lower respiratory tract disease (LRTD) in adults aged 60 years and older. Pfizer announced the topline findings, from the company’s ongoing phase 3 RENOIR clinical trial on Thursday, February 29, 2024.¹ 

Following surveillance during a second RSV season, RENOIR investigators reported vaccine efficacy (VE) against RSV-associated LRTD, defined by at least 3 symptoms, was 77.8% (95% CI, 51.4-91.1). VE in season 1 was 88.9% (95% CI, 53.6-98.7), demonstrating “durable efficacy” across both seasons (~16.4 months of disease surveillance) of 81.5% (95% CI, 63.3-91.6).¹

VE also proved consistent across 2 RSV seasons in less severe LRTD, which was defined by the presence of 2 or more symptoms (from 65.1% to 55.7% in season 1 and 2, respectively).¹

“We are encouraged by the level of protection that we observed after 2 full RSV seasons for Abrysvo,” said Annaliesa Anderson, PhD, senior vice president and chief scientific officer, vaccine research and development at Pfizer, in the company announcement^.1 “This new data indicate that broad and durable protection against both types of RSV that cause disease…is the potential benefit to having a bivalent vaccine.”

No new reports of adverse events were made during the second RSV season; Pfizer continues to conduct postmarketing studies and surveillance programs to further build out the safety profile of the vaccine.

Pfizer plans to submit these new data to both regulatory authorities and scientific journals for publication.

Abrysvo was first approved by the FDA in May 2023 for the prevention of RSV-associated LRTD in adults aged 60 years or older. That was followed in August 2023 by approval for the prevention of RSV-associated LRTD and RSV-associated severe LRTD in infants from birth through age 6 months through the immunization of pregnant individuals between 32- and 36-weeks gestational age. Other steps in the vaccine's history are highlighted below.²

Abrysvo approval history highlights

The company has 2 additional clinical trials evaluating Abrysvo underway: The first is evaluating VE in children aged 2 to 18 years at higher risk for RSV; the second trial is evaluating efficacy in two groups of adults: adults aged 18 to 59 years who are at higher risk for RSV due to underlying medical conditions such as asthma, diabetes, and chronic obstructive pulmonary disease as well as adults aged 18 years and older who are immunocompromised and at high risk for RSV.¹

References

1. Pfizer announces positive top-line data for full season two efficacy of Abrysvo for RSV in older adults. News release. Pfizer. February 29, 2024. Accessed March 1, 2024. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-positive-top-line-data-full-season-two

2. Abrysvo FDA approval history. Drugs.com. Accessed March 1, 2024; last updated August 2023. https://www.drugs.com/history/abrysvo.html