A Study to Describe the Safety and Immunogenicity of a RSV Vaccine in Healthy Adults

The study will describe the safety, tolerability, and immunogenicity of up to 6 RSV vaccine formulations when administered alone or concomitantly with SIIV. Healthy male and female subjects divided into 2 age groups (18-49 years of age and 50-85 years of age in the sentinel cohort and 18-49 years of age and 65-85 years of age in the expanded cohort) will be enrolled. Age groups will run in parallel. Subjects in the sentinel cohort in each age group will receive one of two RSV vaccine formulations at one of 3 antigen dose levels or placebo. Subjects in the expanded cohort in each age group will receive one of two RSV vaccine formulations at one of 3 antigen dose levels with and without SIIV.