An experimental maternal bivalent vaccine against respiratory syncytial virus appears to have high efficacy for preventing severe infection in early infancy, the manufacturer has announced.

Results from Pfizer’s large phase III trial also suggest the respiratory syncytial virus (RSV) vaccine — administered to pregnant women in the late second or third trimester — is well-tolerated in mothers and infants alike.

Although the results are yet to be published in a peer-reviewed journal, a leading paediatric infectious diseases physician says the available data are “encouraging”.

“[They] appear to be meaningful outcomes in terms of preventing significant lower respiratory tract infection in babies,” said Professor Jim Buttery, from the Centre for Health Analytics at the Melbourne Children’s Campus.