Pfizer announces topline data for its bivalent RSV vaccine candidate


Pfizer announced that its bivalent respiratory syncytial virus vaccine—when given to women during pregnancy—has shown effective in protecting infants from reducing severe symptoms during their first 6 months of birth.

During an infant’s first 6 months of life is when they are most vulnerable to severe symptoms. Yesterday on Tuesday, November 1, 2022, Pfizer announced positive top-line data from the MATISSE (Maternal Immunization Study for Safety and Efficacy) trial that investigated its bivalent RSV prefusion candidate, RSVpreF or PF-09628316 when administered to pregnant women to help protect infants from RSV disease after birth.

If approved, Pfizer’s RSV vaccine candidate could be the first maternal vaccine available to help prevent this common and potentially life-threatening respiratory illness in young infants. Pfizer is the only company with an investigational vaccine being prepared for regulatory applications for borth infants through maternal immunization and older adults to help protect against RSV.

The pre-planned, interim efficacy analysis conducted by an external and independent data monitoring committee met the succession criteria for 1 of 2 primary endpoints. The observed efficacy for severe medically attended lower respiratory tract illess was 81% (CI: 40.6%, 96.3%) through the first 90 days of life. Substantial efficacy of 69.4% (CI: 44.3%, 84.1%) was demonstrated for infants over the 6-month follow-up period.

While statistical success criteria were not met for the second primary endpoint, researchers did observe clinically meaningful efficacy for severe medically attended lower respiratory tract illness of 57.1% (CI: 14.7%, 79.8%) in infants from birth through the first 3 months of life. An efficacy of more than 50% (51.3%) (CI: 29.4%, 66.8%) was observed over the 6-month follow up period.

“We are thrilled by these data as this is the first-ever investigational vaccine shown to help protect newborns against severe RSV-related respiratory illness immediately at birth,” said Annaliesa Anderson, Ph.D., aenior vice president and chief scientific officer of vaccine research and development at Pfizer.


Pfizer Announces Positive Top-Line Data of Phase 3 Global Maternal Immunization Trial for its Bivalent Respiratory Syncytial Virus (RSV) Vaccine Candidate | Pfizer. Published 2022. Accessed November 2, 2022.

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