Astra-Sanofi RSV Shot Succeeds in Keeping Babies Out of Hospital

A shot from AstraZeneca Plc and Sanofi that protects babies against a common respiratory virus proved more effective than expected at preventing hospitalizations during its US roll-out.

The injected monoclonal antibody Beyfortus was 90% effective at keeping infants with respiratory syncytial virus out of hospital, according to early surveillance data from the US Centers for Disease Control and Prevention. The data, published Thursday, surpassed the 81% efficacy seen in a late-stage clinical trial, although that trial looked at more patients over a longer period.

The virus known as RSV is the leading cause of hospitalization for babies in the ...