RSV Nirsevimab

About RSV Nirsevimab

Nirsevimab Beyfortus is a long acting monoclonal antibody that protects infants from RSV. Technically not a vaccine, nirsevimab provides passive immunization lasting approximately 5 months, covering the typical RSV season. The FDA approved nirsevimab in July 2023. US health authorities recommended it for young infants entering their first RSV season, and recommendations elsewhere are set by national authorities. Sanofi and AstraZeneca market nirsevimab, which launched in the US at a list price of 495 dollars per dose. Supply shortages initially limited availability. Some infants were instead protected by the maternal RSV vaccine Abrysvo, given to the pregnant person. Nirsevimab demonstrated that monoclonal antibodies can function like vaccines for populations who cannot mount adequate immune responses. The technology was developed at AstraZeneca using YTE half life extension technology. The seasonal nature of RSV and the need for seasonal dosing create unique challenges for implementation and financing.