Efficacy, Immunogenicity, and Safety Study of a Respiratory Syncytial Virus Vaccine in Infants and Toddlers

This study is a phase III, randomized, observer-blind, placebo-controlled, multinational, multi-center study to be conducted in approximately 6300 children 6 months to \< 22 months of age. The purpose of the study is to evaluate the efficacy, immunogenicity, and safety of Respiratory Syncytial Virus Toddler (RSVt) vaccine administered by intranasal route compared to placebo. Eligible participants will be randomized in a 1:1 ratio to receive 2 intranasal administrations of either the RSVt vaccine or placebo. Study duration will be 24 months for each participant. The safety follow-up will start after the first vaccination and up to the end of the study.