Pfizer Touts 85% Efficacy of RSV Vaccine for Adults, Will Seek FDA Approval

In the phase 3 trial, Pfizer’s vaccine was 85.7% effective against respiratory syncytial virus (RSV) defined by 3 or more symptoms among older adults.

Pfizer said Thursday its vaccine for respiratory syncytial virus (RSV) was effective among older adults in a late-stage study and it plans seek approval with the FDA as well as other regulatory authorities around the world.

RSV is estimated to cause about 14,000 annual deaths among older adults in the United States and treatment is limited; there is no vaccine.

According to an interim analysis carried out by an external data monitoring panel, the vaccine was 66.7% effective in preventing against RSV-associated lower respiratory tract illness defined by 2 or more symptoms (96.66% CI, 28.8%-85.8%).

At the more severe disease end point defined as 3 or more symptoms, vaccine efficacy was 85.7% (96.66% CI, 32.0%-98.7%).

It was also found to be well-tolerated with no safety concerns.

The phase 3 clinical trial (NCT05035212) RENOIR (RSV vaccine Efficacy study iNOlder adults Immunized against RSV disease) investigated the bivalent RSV prefusion F vaccine candidate, RSVpreF, in adults 60 years and older. The bivalent vaccine candidate is made up of 2 preF proteins selected to optimize protection against RSV A and B strains.

RENOIR is a global, randomized, double-blind, placebo-controlled study designed to assess the efficacy, immunogenicity, and safety of a single vaccine dose. To date it has enrolled approximately 37,000 participants, randomized to receive 120 mcg RSVpreF or placebo in a 1:1 ratio; enrollment up to approximately 40,000 adults continues in the Southern Hemisphere, Pfizer said in a statement.

Each year it is estimated that 336,000 older adults are hospitalized globally due to RSV, with 177,000 of those occurring in the United States.

The company said it plans to present results of the interim analysis at a future medical congress and will submit the results for peer-review in a scientific journal.

"Scientists and researchers have worked to develop RSV vaccines with little success for over half a century. These findings are an important step in our effort to help protect against RSV disease, and we look forward to working with the FDA and other regulatory agencies to make this vaccine candidate available to help address the substantial burden of RSV disease in older adults," said Annaliesa Anderson, PhD, senior vice president and chief scientific officer, Vaccine Research and Development, Pfizer.