Immunization of Pregnant Women with a Novel Respiratory Syncytial Virus Vaccine: Work in Progress

During the first 3 postnatal months infants are susceptible to pneumonia caused by respiratory syncytial virus (RSV), resulting in >100,000 deaths globally (particularly in settings with poverty, crowding, and air pollution). A monoclonal antibody to RSV fusion protein (F protein) can, through passive immunity, protect high-risk infants from RSV infection. To test whether an investigational RSV vaccine based on F protein is efficacious, investigators randomized 4636 pregnant women at 28 to 36 weeks' gestation to receive a single dose of vaccine or placebo in an international trial sponsored by the manufacturer and the Gates Foundation.

The primary endpoint, RSV-associated medically significant lower respiratory tract infection, was observed …