Human respiratory syncytial virus (RSV) is the most common viral cause of serious acute lower respiratory illness in infants and children under 5 years of age worldwide. This study evaluated the safety, infectivity, and immunogenicity of a single dose of a recombinant live-attenuated RSV vaccine, RSV LID ΔM2-2 1030s, in RSV-seronegative infants 6 to 24 months of age.~Participants were randomly assigned to receive a single dose of the RSV LID ΔM2-2 1030s vaccine or placebo (administered as nose drops) at study entry (Day 0).~Participants could be enrolled in the study between April 1 and October 14 (outside of RSV season) and remained on study until they completed the post-RSV season visit between April 1 and April 30 in the calendar year following enrollment. Participants' total study duration was between 6 to 10 months, depending on when they enrolled in the study. Participants attended several study visits throughout the study, which included blood collection, nasal washes, and/or physical examinations. Participants' parents or guardians were contacted by study staff at various times during the study to monitor participants' health.
The purpose of this study was to evaluate the safety, infectivity, and immunogenicity of a single dose of a recombinant live-attenuated respiratory syncytial virus (RSV) vaccine in RSV-seronegative infants 6 to 24 months of age.~This study was a companion study to CIR 311.