Efficacy and Safety of an mRNA-Based RSV PreF Vaccine in Older Adults

Respiratory syncytial virus (RSV) can cause substantial morbidity and mortality among older adults. An mRNA-based RSV vaccine, mRNA-1345, encoding the stabilised RSV perfusion F glycoprotein, is under clinical investigation. In this ongoing, randomised, double-blind, placebo-controlled, phase 2–3 trial, we randomly assigned, in a 1:1 ratio, adults 60 years of age or older to receive one dose of mRNA-1345 (50 μg) or placebo. The two primary efficacy end points were the prevention of RSV-associated lower respiratory tract disease with at least two signs or symptoms and with at least three signs or symptoms. A key secondary efficacy end point was the prevention of RSV-associated acute respiratory disease. Safety was also assessed.