Nirsevimab (Beyfortus?) in the prevention of RSV bronchiolitis. Decisions based on scientific evidence

Since September 15, 2023, Beyfortus (R) has been available and reimbursed in France with the indication: "prevention of lower respiratory tract infections due to respiratory syncytial virus (RSV) in newborns and infants during their first season of RSV circulation". This indication is based on three randomised, double-blind trials (with distinct objectives) involving populations of infants at very different levels of risk of severe disease. The efficacy of this preventive medicine has been well demonstrated in the "onset of RSV bronchiolitis" occurring within 5 months of treatment. For methodological and biostatistical reasons, its efficacy is scientifically less established for the criterion of "hospitalisation for lower respiratory infection due to RSV", although it remains probable. In terms of safety of use, the risk of a viral mutation likely to render the drug ineffective due to a massive use of this monoclonal antibody is yet unknown. The availability of Beyfortus (R) for low-risk patients (who are by far the most numerous) provides a relevant benefit for infants, their parents who are often frightened by their child's symptoms, and probably for the healthcare system.