RSV Prefusion F Protein-Based Maternal Vaccine - Preterm Birth and Other Outcomes

Area of Science:

• Immunology
• Vaccinology
• Pediatrics

Background:

• Respiratory syncytial virus (RSV) poses a significant threat to infants, necessitating protective strategies.
• Maternal vaccination during pregnancy is a potential approach to confer passive immunity to newborns against RSV disease.
• Efficacy and safety data for a candidate RSV prefusion F protein-based maternal vaccine (RSVPreF3-Mat) were required.

Purpose of the Study:

• To assess the efficacy and safety of the RSVPreF3-Mat vaccine in pregnant women and their infants.
• To evaluate the incidence of RSV-associated lower respiratory tract disease and safety outcomes in infants up to 12 months of age.

Main Methods:

• A phase 3, randomized, placebo-controlled trial was conducted involving pregnant women aged 18-49 years.
• Participants received either RSVPreF3-Mat or placebo between 24 and 34 weeks of gestation.
• Enrollment was stopped early due to observed safety concerns regarding preterm birth.

Main Results:

• Vaccine efficacy against any medically assessed RSV-associated lower respiratory tract disease was 65.5% (95% CI, 37.5 to 82.0).
• Efficacy against severe medically assessed RSV-associated lower respiratory tract disease was 69.0% (95% CI, 33.0 to 87.6).
• A higher risk of preterm birth was observed in the vaccine group (6.8%) compared to the placebo group (4.9%), P=0.01.

Conclusions:

• The RSVPreF3-Mat vaccine demonstrated efficacy in reducing RSV-associated lower respiratory tract disease in infants.
• A significant safety concern was identified: an increased risk of preterm birth in infants born to mothers vaccinated with RSVPreF3-Mat.
• Further investigation into the safety profile, particularly regarding preterm birth, is warranted before widespread maternal RSV vaccination can be considered.