Pfizer's ABRYSVO Vaccine Receives FDA Clearance for Maternal Immunization Against RSV in Newborns

Protecting infants from respiratory syncytial virus (RSV) during their most vulnerable first six months of life has become possible through a groundbreaking maternal vaccination approach. The U.S. Food and Drug Administration has approved ABRYSVO, a bivalent RSV prefusion F vaccine developed by Pfizer, marking the first maternal immunization strategy designed specifically to shield newborns from RSV-caused lower respiratory tract disease.

The Burden of RSV and the Need for Prevention

RSV represents one of the most significant infectious disease threats to infants worldwide. Nearly all children experience an RSV infection by age two, and the virus can cause severe respiratory complications in the youngest patients whose immune systems remain underdeveloped. In the United States alone, approximately 500,000 to 600,000 infants annually suffer from RSV-related lower respiratory tract disease, making it a leading cause of hospitalization in children under one year of age. The virus spreads readily through respiratory secretions and can potentially lead to severe illness or fatal outcomes.

How ABRYSVO Works Through Maternal Immunization

The newly approved ABRYSVO vaccine employs an innovative approach: pregnant individuals receive immunization between 32 and 36 weeks of gestational age. The vaccine’s two preF proteins target both RSV A and B strains, optimizing protection against the disease’s most common variants. Antibodies generated through this maternal vaccination transfer to the developing fetus, providing passive protection from birth through approximately six months of age—the critical window when infants face the highest risk of severe RSV complications.

Clinical Evidence Supporting FDA Approval

The FDA’s decision rested on robust evidence from the MATISSE trial (NCT04424316), a randomized, double-blind, placebo-controlled Phase 3 study involving more than 7,000 pregnant participants and encompassing over 14,000 total participants when including their infants. This comprehensive research demonstrated that ABRYSVO was both safe and effective at preventing lower respiratory tract disease and severe lower respiratory tract disease caused by RSV in infants born to vaccinated mothers. Data from this pivotal study were published in The New England Journal of Medicine in April 2023, providing peer-reviewed validation of the vaccine’s efficacy and safety profile.

Clinical Significance and Healthcare Impact

Medical experts recognize this approval as transformative for pediatric health. As one clinical professor in pediatric infectious diseases noted, newborns and young infants require protection during the period when their immune defenses are still developing. ABRYSVO eliminates delays in RSV protection by providing immunity from the moment of birth, offering healthcare providers a new tool to prevent severe disease during an infant’s most fragile months. This represents a major advance in preventive medicine for vulnerable populations.

Pfizer’s Expanded RSV Vaccine Portfolio

Pfizer is currently the only pharmaceutical company with RSV vaccines addressing multiple populations. In May 2023, the FDA previously approved ABRYSVO for adults 60 years of age and older to prevent RSV-associated lower respiratory tract disease. Following this clearance, the CDC’s Advisory Committee on Immunization Practices issued recommendations for vaccine use in older adults. Regulatory approvals and reviews are also underway in Europe, Canada, and Japan, indicating broad recognition of the vaccine’s public health importance across multiple healthcare systems.