Evaluating the Infectivity, Safety and Immunogenicity of a Recombinant Live-Attenuated Respiratory Syncytial Virus Vaccine, LID/ΔM2-2/1030s, in RSV-Seronegative Infants and Children 6 to 24 Months of Age

The purpose of this study is to evaluate the infectivity, safety, and immunogenicity of a single dose of a recombinant, live-attenuated respiratory syncytial virus (RSV) vaccine, LID/ΔM2-2/1030s, in RSV-seronegative infants and children 6 to 24 months of age.

This study will evaluate the infectivity, safety, and immunogenicity of a single dose of a recombinant, live-attenuated respiratory syncytial virus (RSV) vaccine, LID/ΔM2-2/1030s, in RSV-seronegative infants and children 6 to 24 months of age. Participants will be randomly assigned to one of two groups to receive a single dose of intranasal RSV LID/ΔM2-2/1030s vaccine or placebo at study entry (Day 0). Group 1 (intensive) and Group 2 (less intensive) will differ only in the frequency of study visits and nasal swab collections. Participants will receive study product between April 1 and October 15, outside of the RSV season, and will remain on the study until they complete the post-RSV season visit between April 1 and April 30 in the calendar year following enrollment. Participants' total study duration is between 6 and 13 months, depending upon time of enrollment. Participants will attend several study visits throughout the study, which may include blood collection, nasal swabs, and physical examinations. Some of these visits may be remote if a stay at home order is put in place after enrollment.