FDA Advisory Committee Supports Vaccine Candidate for Severe RSV in Older Adults

The FDA set a Prescription Drug User Fee Act for May 2023 for Pfizer’s respiratory syncytial virus bivalent vaccine candidate.

A majority of the FDA’s Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted that Pfizer’s new respiratory syncytial virus (RSV) bivalent vaccine candidate PF-06928316 (RSVpreF)—currently under review to prevent acute respiratory disease and lower respiratory tract disease caused by RSV in adults aged 60 years and older—is safe and effective.1

The VRBPAC, which provides non-binding recommendations to the FDA, voted 7 to 4 in favor of the safety and efficacy of RSVpreF.1

“We are encouraged by the outcome of today’s VRBPAC meeting as it is a testament to the strength of our science and dedication to bringing this important vaccine candidate to the market,” said Annaliesa Anderson, PhD, senior vice president and chief scientific officer, Vaccine Research and Development, Pfizer, in a press release.1

Clinical Trials of Bivalent Vaccine Candidate RSVpreF

The novel vaccine RSVpreF produced efficacy of 66.7% (96.66% CI: 28.8%, 85.8%) against respiratory syncytial virus-associated lower respiratory tract illness (LRTI-RSV) as defined by 2 or more symptoms. This finding prompted researchers to examine the more severe disease primary endpoint of LRTI-RSV as defined by 3 or more symptoms, which showed an efficacy rate of 85.7% (96.66% CI: 32.0%, 98.7%).

RSV is a contagious virus and a common cause of respiratory illness that can affect the breathing passages and lungs of infected individuals. Further, RSV is potentially life-threatening to infants. Among older US adults, RSV infections account for approximately 60,000–120,000 hospitalizations and 6000–14,000 deaths each year. In US children younger than 5 years of age, RSV infections are responsible for approximately 2.1 million outpatient visits and 58,000–80,000 hospitalizations each year.

Older adults are particularly at risk of “serious illness, hospitalization, or even death,” according to Anderson. There is no targeted prophylactic, therapeutic, or vaccine options for RSV in older adults.1

According to Pfizer, RSVpreF is based on foundational basic science discoveries, such as findings from the National Institutes of Health (NIH), detailing the crystal structure of prefusion F, a vital form of the viral fusion protein (F) used by RSV to attack human cells. NIH research indicates that antibodies specific to the prefusion form had high efficacy preventing viral infection. This indicates that a prefusion F-based vaccine may provide optimal protection against RSV, according to Pfizer.

The FDA committee based their recommendation on data from the RENOIR (RSV vaccine Efficacy study iN Older adults Immunized against RSV disease) study. RENOIR evaluated the efficacy, immunogenicity, and safety of single-dose RSVpreF for adults aged 60 years and older. The study included more than 37,000 participants who received 120μg of RSVpreF or placebo.2

The primary endpoint was severe respiratory tract illness (LRTI-RSV), defined as having 3 or more associated symptoms. RSVpreF met the primary endpoint, showing 85.7% efficacy at protecting against severe disease.2

The vaccine candidate includes recombinant RSV prefusion F, a form of viral fusion protein F. Antibodies in prefusion F have been shown to be effective at blocking viral infection, leading investigators to hypothesize its efficacy at protecting against RSV.1

The analysis showed that RSVpreF produced vaccine efficacy of 66.7% (96.66% CI: 28.8%, 85.8%) against RSV-associated lower respiratory tract illness (LRTI-RSV) as defined by 2 or more symptoms. This finding prompted researchers to examine the more severe disease primary endpoint of LRTI-RSV as defined by 3 or more symptoms, which showed an efficacy rate of 85.7% (96.66% CI: 32.0%, 98.7%). Additionally, the trial showed that the investigational vaccine was well-tolerated with no safety concerns, according to Pfizer.2

Pfizer is the only company currently investigating an RSV vaccine candidate to protect vulnerable, older adults. The vaccine candidate would be indicated to protect infants (via immunizing the maternal adult) as well. The FDA granted the treatment with Breakthrough Therapy Designation to prevent RSV-associated lower respiratory tract disease caused by RSV in March 2022.1

“We look forward to working with the FDA as it completes the review of our application,” Anderson said in the press release.1


  1. Pfizer. Pfizer Receives Positive FDA Advisory Committee Votes Supporting Potential Approval for Vaccine Candidate to Help Combat RSV in Older Adults. News Release. February 28, 2023. Accessed February 29, 2023. https://www.businesswire.com/news/home/20230228005903/en
  2. Pfizer. Pfizer Announces Positive Top-Line Data from Phase 3 Trial of Older Adults for its Bivalent Respiratory Syncytial Virus (RSV) Vaccine Candidate. News Release. August 25, 2022. Accessed March 1, 2023. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-positive-top-line-data-phase-3-trial-older
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