The FDA’s approval of Pfizer Inc’s bivalent respiratory syncytial virus (RSV) prefusion F (RSVpreF) vaccine Abrysvo to prevent lower respiratory tract disease caused by RSV in individuals 60 years of age and older is based on foundational basic science discoveries. These discoveries include findings from the National Institutes of Health (NIH) that detail the crystal structure of prefusion F, a crucial form of the viral fusion protein (F) used by RSV to attack human cells. NIH research suggests that antibodies specific to the prefusion form have shown high efficacy in preventing viral infection. Pfizer believes that a prefusion F-based vaccine may offer optimal protection against RSV.
A vaccine to help prevent RSV had been an elusive public health goal for more than half a century. Today’s approval is a monumental step forward in delivering on Pfizer’s commitment to help alleviate the significant burden of RSV in higher-risk populations, which includes older adults,” said Annaliesa Anderson, PhD, senior vice president and chief scientific officer, Vaccine Research and Development, Pfizer, in a press release. “Abrysvo will address a need to help protect older adults against the potentially serious consequences of RSV disease. We are extremely grateful to the clinical trial participants, study investigator teams and our dedicated Pfizer colleagues for their roles in making this vaccine available.
Key Findings
The FDA approval was based on data obtained from the RENOIR (RSV vaccine Efficacy study iNOlder adults Immunized against RSV disease) trial, a phase 3 study (NCT05035212). This global, randomized, double-blind, placebo-controlled trial aimed to evaluate the efficacy, immunogenicity, and safety of a single dose of RSVpreF in individuals aged 60 and above. Around 37,000 participants were randomly assigned in a 1:1 ratio to receive either RSVpreF 120 μg or placebo. Pfizer had previously announced positive top-line results from an interim efficacy analysis of the RENOIR trial.
The analysis revealed that RSVpreF demonstrated a vaccine efficacy of 66.7% (96.66% CI: 28.8%, 85.8%) against RSV-associated lower respiratory tract illness (LRTI-RSV) defined by the presence of two or more symptoms. This encouraging result led researchers to examine the primary endpoint of more severe disease, defined as LRTI-RSV with three or more symptoms, which showed an efficacy rate of 85.7% (96.66% CI: 32.0%, 98.7%). Furthermore, the trial demonstrated that the investigational vaccine was well-tolerated, with no safety concerns reported, according to Pfizer.
In March 2022, RSVpreF was granted Breakthrough Therapy Designation by the FDA for this indication, and in December 2022, it received Priority Review designation.