Safety and Immunogenicity Study to Evaluate Single- or Two-Dose Regimens Of RSV F Vaccine With and Without Aluminum Phosphate or Matrix-M1™ Adjuvants In Clinically-Stable Older Adults

This is a randomized, observer-blind, trial in clinically-stable older adults. Up to 300 eligible older adults 60 through 80 years of age will be enrolled at a 1:1 ratio into multiple dose/formulation treatment arms. Safety and immunogenicity data through Day 56 will be used to select a vaccine candidate to potentially evaluate in a Part 2 study. Proportions of subjects in various strata will not be pre-specified and the goal will be to achieve an approximately equal distribution of subjects with these characteristics across the treatment groups. Serology measures consistent with the study outcomes will be reported.