FDA Action Date Set for Pfizer RSV Vaccine Candidate


The vaccine would be administered to pregnant people to protect newborns from RSV.

The FDA has accepted for review the Biologics License Application for Pfizer’s respiratory syncytial virus (RSV) vaccine candidate RSVpreF (PF-06928316) that would be administered to pregnant people so their newborns can avoid medically attended lower respiratory tract illness caused by RSV.1 The action date is set for August 2023.

This is the next step in the administrative process for RSVpreF following its Breakthrough Therapy Designation by the FDA in March 2022.

In November 2022, Pfizer announced positive top-line results of the MATISSE study (NCT04424316),2 a phase 3 clinical trial measuring the effectiveness of the vaccine. The study enrolled nearly 7400 pregnant people randomly assigned to receive either 120 µg of Pfizer’s RSVpreF or placebo during the late second to third trimester of their pregnancy.2 Participants were tracked 6 months after delivery. The study—which began in June 2020 and spanned multiple RSV seasons —took place in 18 countries.

When the study concluded, RSVpreF demonstrated an efficacy of 81.8% in protecting newborns against severe medically attended lower respiratory tract infection 90 days after birth, and an efficacy of 69.4% after 6 months. Results of an interim efficacy analysis showed that RSVpreF met 1 of 2 primary endpoints, with an observed efficacy for severe medically attended lower respiratory tract illness of 81.8% (95% CI, 40.6%-96.3%) for the first 90 days of life. A “substantial efficacy” of 69.4% (95% CI, 44.3%-84.1%) was demonstrated over the 6-month follow-up period.2

Clinically meaningful, but not statistically successful, efficacy was noted for medically attended lower respiratory tract illness through the first 90 days of life and the 6-month follow-up period (57.1% and 51.3%, respectively).2

“If approved, RSVpreF would help protect infants at their first breath from the devastating effects of this infectious disease, which though well-known, has been particularly evident throughout this RSV season,” said Pfizer’s senior vice president and chief scientific officer, vaccine research and development, Annaliesa Anderson, PhD. “We look forward to progressing the review of Pfizer’s RSV maternal vaccine candidate with the FDA and other regulatory authorities, given its significant potential to positively contribute to global health in the prevention of RSV in infants.”

RSV infections are the cause of approximately 2.1 million outpatient visits and 58,000 hospitalizations each year among children younger than age 5 in the United States, and “virtually all” children experience an RSV infection by age 2.1 Worldwide, RSV is responsible for the death of approximately 102,000 children per year, with the vast majority of those deaths occurring in developing countries.

Outside of the United States, the European Medicines Agency (EMA) has accepted Pfizer’s marketing authorization application for RSVpreF for use in older adults, who also have an increased risk for RSV. In the United States, up to 100,000 adults over 65 years of age are hospitalized each year due to RSV, and anywhere from 6000 to 10,000 die due to the virus. A decision on whether RSVpreF is an option for older adults will likely be made later this year.


1. US FDA accepts Biologics License Application for Pfizer’s respiratory syncytial virus maternal caccine candidate for priority review. [LB20] News Release. Pfizer. February 20, 2023. Accessed February 22, 2023. https://www.pfizer.com/news/press-release/press-release-detail/us-fda-accepts-biologics-license-application-pfizers
2. Pfizer announces positive top-line data of phase 3 global maternal immunization trial for its bivalent respiratory syncytial virus (RSV) vaccine candidate. News Release. Pfizer. November 1, 2022. Accessed February 22, 2023. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-announces-positive-top-line-data-phase-3-global

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