A Study to Characterize the Safety and Immunogenicity of AZD6489 in Participants 60 Years of Age and Older (ARIES)

This Phase I/II clinical study will be conducted in the US at approximately 5 sites. The study is a randomized, double-blind, active-controlled study to characterize the safety and immunogenicity of a single dose of AZD6489 in adults ≥ 60 years of age. Two dose levels of AZD6489 will be assessed. Approximately 160 participants will be randomized and stratified by age group and previous receipt of RSV vaccine. Participants will be randomized/dosed to receive AZD6489, licensed RSV vaccine #1, or licensed RSV vaccine #2. The study is split into 2 cohorts based on the 2 dose levels of AZD6489 being studied. For each cohort, an initial sentinel group of 8 participants will be followed up for safety via a telephone or teleconference call, approximately 48 hours post-study intervention, and the safety data will be evaluated by the SRC in order to provide a recommendation to continue randomization and vaccination for the remaining participants in that cohort. An ESDR of all available safety data through 7 days post-vaccination of Cohort 1 will be conducted. Randomization of Cohort 2 will be allowed only after the ESDR of Cohort 1 participants has been completed and the results support that the safety profile is acceptable. This study includes 5 in-clinic study visits. The duration of each participant's involvement in the study will be approximately 12 months following the administration of study intervention. Safety will be assessed for the duration of the study. Blood will be taken for immunological and safety assessments as per SoA.