Respiratory Syncytial Virus Vaccination during Pregnancy and Effects in Infants

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections in infants. This randomized, observer-blind, placebo-controlled phase 3 trial evaluated the efficacy of an RSV fusion (F) protein nanoparticle vaccine administered to pregnant women (28–36 weeks of gestation) in preventing RSV-associated illness in their infants. A total of 4636 women were enrolled, with 4579 live births. By 90 days of life, RSV associated medically significant lower respiratory tract infection occurred in 1.5% of infants in the vaccine group versus 2.4% in the placebo group (vaccine efficacy: 39.4%; 97.52% CI, –1.0 to 63.7). Vaccine efficacy against severe hypoxemia and hospitalization for RSV associated illness was 48.3% and 44.4%, respectively. Local injection site reactions were more common with the vaccine (40.7% vs. 9.9%), but systemic adverse events were similar between groups. While the primary efficacy criterion was not met, the findings suggest potential benefits of maternal RSV vaccination, warranting further study.

Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract infections in infants. This randomized, observer-blind, placebo-controlled phase 3 trial evaluated the efficacy of an RSV fusion (F) protein nanoparticle vaccine administered to pregnant women (28–36 weeks of gestation) in preventing RSV-associated illness in their infants. A total of 4636 women were enrolled, with 4579 live births. By 90 days of life, RSV associated medically significant lower respiratory tract infection occurred in 1.5% of infants in the vaccine group versus 2.4% in the placebo group (vaccine efficacy: 39.4%; 97.52% CI, –1.0 to 63.7). Vaccine efficacy against severe hypoxemia and hospitalization for RSV associated illness was 48.3% and 44.4%, respectively. Local injection site reactions were more common with the vaccine (40.7% vs. 9.9%), but systemic adverse events were similar between groups. While the primary efficacy criterion was not met, the findings suggest potential benefits of maternal RSV vaccination, warranting further study.