Pfizer Announces Positive Findings in Phase 3 Trial of Bivalent Respiratory Syncytial Virus Vaccine Candidate in Older Adults


The vaccine candidate is composed of 2 preF proteins selected to optimize protection against the RSV A and B strains.

New data from the phase 3 RENOIR trial shows promise for Pfizer’s investigative bivalent respiratory syncytial virus (RSV) vaccine candidate in older adults, according to a company press release.

The phase 3 RENOIR trial is a global, randomized, double-blind, placebo-controlled study designed to assess the efficacy, immunogenicity, and safety of a single dose of the vaccine in adults 60 years of age and older. To date, the trial has enrolled approximately 37,000 participants, randomized 1:1 to receive either placebo or 120 μg of the investigative vaccine, called RSVpreF.

The vaccine candidate is composed of 2 preF proteins selected to optimize protection against the RSV A and B strains. RSV is characterized by several respiratory symptoms, which can vary from mild to severe, and more severe disease typically includes more symptoms. The virus can affect the lungs and breathing passages of infected individuals and can be potentially life-threatening for older adults or individuals with certain medical conditions.

According to the press release, experts estimate that 336,000 older adults are hospitalized globally each year due to RSV. In the United States alone, RSV infections in older adults account for approximately 177,000 hospitalizations and 14,000 deaths annually. There are currently no prophylactic or therapeutic options for RSV in older adults, and treatments are currently limited to supportive care.

A pre-planned, interim analysis of the vaccine’s efficacy to assess protection against RSV-associated lower respiratory tract illness (LRTI) defined by 2 or more symptoms found an efficacy of 66.7%. This positive result allowed Pfizer to look at the more severe disease primary endpoint of LRTI-RSV, which was defined by 3 or more symptoms. According to the study, the efficacy of the vaccine in this endpoint was 85.7%.

“We are delighted that this first bivalent RSV candidate, RSVpreF, was observed to be efficacious in our clinical trial against this disease, which is associated with high levels of morbidity and mortality in older adults,” said Annaliesa Anderson, PhD, senior vice president and chief scientific officer of vaccine research and development at Pfizer, in the press release.

The external data monitoring committee also indicated that the vaccine was well-tolerated, with no safety concerns. Based on all of these findings, Pfizer plans to submit a Biologics License Application to the FDA for the vaccine and to prepare submissions for other regulatory authorities in the coming months.

“Scientists and researchers have worked to develop RSV vaccines with little success for over half a century,” Anderson said in the press release. “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.”

In March 2022, the vaccine received Breakthrough Therapy Designation from the FDA for the prevention of RSV-associated lower respiratory tract disease caused by RSV in infants from birth up to 6 months of age by active immunization of pregnant women. This designation was primarily informed by the results of the phase 2b proof-of-concept study of RSVpreF.

In June 2020, the company announced the initiation of a multicenter, international phase 3 clinical trial, MATISSE, evaluating the efficacy and safety of a single dose of RSVpreF when administered to pregnant individuals to help protect infants from RSV after birth. This trial remains ongoing, according to the press release.


Pfizer Announces Positive Top-Line Data from Phase 3 Trial of Older Adults for its Bivalent Respiratory Syncytial Virus (RSV) Vaccine Candidate. News release. Pfizer; August 25, 2022. Accessed August 25, 2022.

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