 AstraZeneca PLC LSE:AZN and Sanofis Beyfortus nirsevimab immunisation has been approved in the EU for the prevention of respiratory syncytial virus RSV lower respiratory tract infection LRTI in infants during their first RSV season. Beyfortus is the first and only single-dose RSV passive immunisation for the broad infant population, including those born healthy or with specific health conditions, AstraZeneca said in a statement. 