- RSV (Respiratory Syncytial Virus)
- RSV Preventive Antibody Products
What is clesrovimab preventive antibody and how well does it work?
Clesrovimab (Enflonsia, Merck) is a preventive antibody product approved in mid-2025 to be administered intramuscularly as a single 105 mg dose to infants from age 0 days to age 8 months and 0 days either before or during their first RSV season. It is recommended for use as an option for prevention of serious lower respiratory tract infection with RSV in infants. There is no preference between clesrovimab and nirsevimab (Beyfortus, Sanofi) for eligible infants. However, only nirsevimab is approved for high-risk children age 8 through 19 months entering their second RSV season.
Clinical trials demonstrated clesrovimab had benefits similar to nirsevimab, with a 60% reduced risk of medically attended lower-respiratory tract illness (MALRI) caused by RSV and an 84% reduced risk of hospitalization with RSV LRI during the 150 days after administration.
