Respiratory Syncytial Virus (RSV) infection can cause mild, cold-like symptoms but can be serious in some cases. RSV vaccination is available, but vaccination during pregnancy and its effects on infants are unknown. The objective of this study is to investigate the effects of RSV vaccination during pregnancy on infants. 

This is a randomized study that included a total of 4,636 healthy pregnant women at 28-36 weeks of gestation. The participants were randomly assigned in a 2:1 ratio to receive a single intramuscular dose of RSV vaccine or placebo. After delivery, the infants were followed for 180 days. The primary outcome of the study was RSV-associated lower respiratory tract infection up to 90 days of life.

During the first 90 days of life, 1.5% of infants in the vaccine group had significantly lower tract respiratory infection, compared to 2.4% in the placebo group. The percentages for hospitalization for RSV-related respiratory disease for the vaccine and the placebo group were 2.1% and 3.7%, respectively.

The research concluded that RSV F protein vaccination in pregnant women did not meet the success criterion for efficacy against RSV-associated respiratory disorder. Thus, more study is required to confirm the effectiveness of the RSV vaccine in the prevention of RSV infection in infants.