French healthcare company Sanofi S.A. (Euronext Paris:SAN) (Nasdaq:SNY) reported on Monday that a universal respiratory syncytial virus immunisation programme using Beyfortus (nirsevimab) was associated with a statistically significant reduction in RSV-related hospitalisations in the second RSV season among infants immunised during their first season.

Conducted in Galicia, Spain, the real-world population study evaluated outcomes across two consecutive RSV seasons. Findings have been published in The Lancet Infectious Diseases, and will be presented at the RSVVW '26 conference in Rome, Italy.

Coverage reached 94.4% (11,796 of 12,492 eligible infants), with an 85.9% reduction in RSV-related lower respiratory tract infection hospitalisations in the first season and 55.3% fewer hospitalisations in the second season among infants immunised during infancy.

The analysis also showed reductions in first-season primary care consultations, including 30.8% for acute bronchitis or bronchiolitis, 33.4% for lower respiratory tract infections, and 27.7% for wheezing or asthma. Among infants previously hospitalised due to RSV, second-season rehospitalisations declined by 78.2% for RSV-related cases and 62.4% for lower respiratory tract infections. The data support the hypothesis that preventing severe RSV infection during early lung development may make infants less prone to subsequent admissions from either RSV or other infections.