FDA Panel Supports Bivalent RSV Maternal Vaccine Candidate

Based on available scientific evidence, the Food and Drug Administration’s (FDA) Vaccines and Related Biological Products Advisory Committee voted in favor of Pfizer’s unadjuvanted bivalent respiratory syncytial virus (RSV) prefusion F vaccine candidate (RSVpreF or PF-06928316) for the prevention of medically attended lower respiratory tract disease (MA-LRTD) and severe MA-LRTD, caused by RSV, in infants from birth up to 6 months of age by active immunization of pregnant individuals. The panel voted 14 to 0 on effectiveness and 10 to 4 on safety.

The vaccine candidate consists of 2 prefusion F proteins selected to optimize protection against RSV A and B. The primary data to support safety and efficacy came from the randomized, double-blind, placebo-controlled phase 3 MATISSE trial (ClinicalTrials.gov Identifier: NCT04424316), which included approximately 7400 pregnant individuals (≤49 years of age) who were between 24 and 36 weeks of gestation.  Study participants were randomly assigned to receive a single dose of RSVpreF (n=3695) or placebo (n=3697).

Results showed vaccine efficacy of 81.8% (99.5% CI, 40.6-96.3) against severe medically attended lower respiratory tract illness (MA-LRTI) in infants from birth through the first 90 days of life (6 cases in the vaccine group and 33 cases in the placebo group). Efficacy of 69.4% (97.58% CI, 44.3-84.1) was observed over the 6-month follow-up period (19 cases in the vaccine group and 62 cases in the placebo group).

While the second primary endpoint did not meet statistical significance, vaccine efficacy against MA-LRTI was reported to be 57.1% (99.5% CI, 14.7-79.8) in infants from birth through the first 90 days of life and 51.3% (97.58% CI, 29.4-66.8) over the 6-month follow up period.

As for safety, no meaningful differences were observed between the groups within 1 month after vaccination. Adverse events in infants were reported at similar frequency between the vaccine and placebo groups. The panel did note an imbalance in the rates of premature births (5.7% in the vaccine group vs 4.7% in the placebo group) and premature delivery (5.6% in the vaccine group vs 4.7% in the placebo group). Similar imbalances were observed in a phase 2 study.

Commenting on the committee vote, Annaliesa Anderson, PhD, Senior Vice President and Chief Scientific Officer, Vaccine Research and Development, Pfizer, said: “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 6 months of life. 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 6 months of life from this potentially serious infection.”

A regulatory decision is expected in August 2023. While not bound by the committee’s recommendations, the FDA does take them into consideration when making decisions on approval.

This article originally appeared on MPR