FDA Advisory Group Votes in Favor of Pfizer Investigational Maternal RSV Vaccine Candidate

An advisory committee to the US Food and Drug Administration on Thursday made a positive recommendation to the agency on a first-ever maternal vaccine against respiratory syncytial virus (RSV) in infants from birth up to age 6 months.

The Vaccines and Related Biological Products Advisory Committee (VRBPAC) voted unanimously (14 to 0) on the efficacy of Pfizer’s investigational bivalent respiratory syncytial virus (RSV) prefusion F vaccine candidate RSVpreF and 10 to 4 on the vaccine's safety when given to pregnant patients in the second or third trimester, according to a news release from Pfizer.

Despite the 4 "no" votes from the committee on the question of whether data presented demonstrated an adequate safety profile for the vaccine, the FDA confirms a PUDFA date of August 2023.

The FDA in February 2022 granted RSVpreF Breakthrough Therapy Designation. In November 2022, the company announced positive topline data from the pivotal phase 3 MATernal Immunization Study for Safety and Efficacy (MATISSE) clinical trial that demonstrated the vaccine’s clinically meaningful efficacy of 57.1% against nonsevere medically-attended lower respiratory tract disease (MA-LRTD) and 81.8% efficacy against severe MA-LRTD in infants from birth through first 90 days of life. These data were among the scientific evidence Pfizer presented to the VRBAC and on which it based its recommendation.

“We are encouraged by the outcome of today’s VRBPAC meeting as it is a critical step forward in the scientific community’s long-sought-after goal to help prevent RSV disease in infants during their most vulnerable first six months of life,” said Annaliesa Anderson, PhD, Pfizer senior vice president and chief scientific officer, vaccine research and development. “If approved, our RSV vaccine candidate has the potential to be the first maternal immunization vaccine to help protect infants at first breath through their first six months of life from this potentially serious infection.”

It is important to note that preterm birth, birth at <37 weeks’ gestation, was reported in 5.7% of infants in the trial’s vaccine group and 4.7% of infants in a placebo group. The difference, according to a Pfizer FDA briefing document, while numerically higher, was not found statistically significant. Low birth weight in both the treatment and placebo groups also was reported and noted to be similar in both: RSVpreF (5.1%) and placebo (4.3%).

RSV is a common cause of respiratory illness and in the US leads to 500- to 600 000 cases of MA-LRTD in infants younger than age 12 months.