Used for the prevention of severe respiratory syncytial virus (RSV) infections in high-risk infants and young children, particularly those with premature birth, chronic lung disease, or congenital heart defects. It works by binding to the RSV fusion protein, preventing viral entry into host cells. Administered monthly during RSV season via intramuscular injection, it reduces the incidence of serious lower respiratory tract disease and hospitalization. Not used for treatment of active RSV infection or for general immunization.