Use of Clesrovimab for Prevention of Severe Respiratory Syncytial Virus–Associated Lower Respiratory Tract Infections in Infants: Recommendations of the Advisory Committee on Immunization Practices — United States, 2025

Before the introduction of universal respiratory syncytial virus (RSV) immunization recommendations for infants, RSV was the leading cause of hospitalization among infants in the United States. Since 2023, CDC's Advisory Committee on Immunization Practices (ACIP) has recommended that all infants be protected against RSV-associated lower respiratory tract infection (LRTI) through either 1) maternal RSV vaccination during pregnancy (Abrysvo, Pfizer) or 2) administration of nirsevimab (Beyfortus, Sanofi and AstraZeneca), a long-acting RSV monoclonal antibody, to the infant. In June 2025, the Food and Drug Administration licensed clesrovimab (Enflonsia, Merck), a second long-acting RSV monoclonal antibody, for prevention of RSV-associated LRTI in infants. Since September 2024, the ACIP Maternal/Pediatric RSV Work Group has reviewed evidence regarding the safety and efficacy of clesrovimab use in infants. On June 26, 2025, ACIP recommended clesrovimab as a second long-acting monoclonal antibody product that could be used as an alternative to nirsevimab for prevention of RSV-associated LRTI among infants aged <8 months who are born during or entering their first RSV season and who are not protected through maternal RSV vaccination. All infants should be protected against RSV-associated LRTI through use of one of these three products (i.e., maternal RSV vaccination or administration of nirsevimab or clesrovimab to the infant). No one product is preferred; the choice should be guided by parent preference, product availability, and timing of the infant's birth relative to the RSV season.