RSV Immunoprophylaxis

Nirsevimab and clesrovimab are single-dose extended half-life monoclonal antibodies with phase 3 efficacy greater than 75%. The main exposure categories are maternal RSV vaccine and infant monoclonal antibody prophylaxis. Substantially higher uptake is required of maternal vaccination than of direct infant immunoprophylaxis to achieve equivalent RSV disease burden reductions. Postlicensure effectiveness may differ from clinical trial efficacy because of administration timing, host factors, pharmacokinetics, immune responses, healthcare access, and viral evolution. Historical uptake for analogous maternal vaccine programmes such as influenza has been approximately 50%, constrained by socioeconomic disparities and hesitancy. In September 2024, the UK launched maternal RSV vaccination for all pregnant women beyond 28 weeks' gestation, conferring passive immunity to infants through transplacental antibody transfer. Maternal RSV prefusion F vaccination protects infants through transplacental antibody transfer. The protocol evaluates maternal RSV vaccination and infant monoclonal antibody prophylaxis for preventing medically attended RSV infection in infants aged 12 months or younger. T…