Nirsevimab for respiratory syncytial virus prevention: A comprehensive product review.

Infant RSV prevention is undergoing a public-health paradigm shift toward scalable, broad-eligibility passive immunization. This review examines nirsevimab (Beyfortus®), a long-acting recombinant IgG1κ monoclonal antibody targeting the conserved site Ø of prefusion RSV F protein. Its extended half-life enables season-long protection with a single dose, overcoming key limitations of palivizumab. A validated manufacturing platform and stringent release specifications ensure consistent quality and potency. Pivotal trials demonstrated high efficacy against RSV-associated lower respiratory tract infection hospitalization (RSVH), while the pragmatic HARMONIE trial confirmed an 83.2% reduction in RSVH under routine conditions. Postlicensure studies across multiple countries report 70-90% effectiveness against RSVH and substantial reductions in intensive care admissions. Comparative 2024-2025 data further suggest greater protection than maternal RSVpreF vaccination. Nirsevimab represents a scalable public-health intervention that can be used alone or complement maternal RSV vaccination, warranting continued surveillance of effectiveness, safety, and viral escape.