Safety and Immunogenicity of CodaVax-RSV in Seropositive and Seronegative Children

This study is a Phase 1, randomized, double-blind, placebo-controlled, dose-escalation clinical trial to evaluate the safety of and immune response to CodaVax-RSV in healthy children. They will be vaccinated in spring to early autumn 2023 and followed through the 2023-24 RSV season. 18 children aged 2 to 5 years who are RSV-seropositive (have antibodies to RSV) and 33 children aged 6 months to \< 2 years who are RSV-seronegative (do not have antibodies to RSV) will be enrolled in escalating-dose cohorts. A safety committee will review the safety profile of each dosing group before the next dose-escalation. Children will receive 2 doses of the vaccine at one of several dose levels or placebo (saline solution with no active ingredient) as nose drops; doses will be 28 days apart. A parent/guardian will record temperature and other conditions in a diary daily for 7 days after each dose. The parent/guardian will be contacted by telephone on the day after Dose 1 for safety assessment and review of the diary data. Children will return to the clinic 3, 7, 14, and 28 days after each dose. The parent/guardian will then be contacted by telephone monthly until 1 year after the second dose. Study procedures include physical examinations, vital signs, and collections of blood and nose/throat swab samples to look at safety of the vaccine and to analyze body's immune response.