RSV vaccine effective in infants when administered during pregnancy

A bivalent RSV prefusion F protein–based (RSVpreF) vaccine is effective against medically attended severe respiratory syncytial virus (RSV)–associated lower respiratory tract infection in infants when administered during pregnancy, according to a recent study published in The New England Journal of Medicine.

Researchers conducted a phase 3, double-blind trial in 18 countries. Participating pregnant women at 24 to 36 weeks’ gestation were randomly assigned 1:1 to receive either a single intramuscular injection of 120 μgbivalent RSVpreF vaccine or placebo.

Medically attended severe RSV-associated lower respiratory tract illness was the first primary measure of the study. The second was medically attended RSV-associated lower respiratory tract illness measured in infants aged 90, 120, 150, and 180 days. A lower confidence interval boundary for vaccine efficacy over 20% was considered successful for the primary measures.

There were 3682 maternal participants in the vaccine group and 3676 in the placebo group. For the vaccine group, 3570 infants were evaluated, along with 3558 for the placebo group. 

In the vaccine group, medically attended severe lower respiratory tract illness was seen in 6 infants within 90 days after birth and 19 within 180 days, compared to 33 within 90 days and 62 within 180 days in the placebo group. Medically attended RSV-associated lower respiratory tract illness was seen in 24 infants in the vaccine group and 56 in the placebo group within 90 days.

The statistical success criterion was met for medically attended severe lower respiratory tract illness, but not medically attended RSV-associated lower respiratory tract illness. Mothers and infants aged up to 24 months did not show safety signals. The vaccine and placebo groups had similar rates of adverse event incidence within 1 month after injection or 1 month after birth.

Reference

Kampmann B, Madhi SA, Munjal I, et al. Bivalent prefusion F vaccine in pregnancy to prevent RSV illness in infants. The New England Journal of Medicine. 2023. doi:10.1056/NEJMoa2216480