A Randomized, Double-blind, Placebo-controlled Phase 1/2a Study for Safety and Immunogenicity Evaluations for Regimen Selection of Ad26.RSV.preF and/or RSV preF Protein Combinations Followed by Expanded Safety Evaluation in Adults Aged 60 Years and Older

The purpose of this study for:Cohort 1 and Cohort 2: to assess the safety and reactogenicity of the intramuscular one- and two-dose regimens, with a booster at Month 12 (Cohort 1) and to select a regimen for Cohort 3.Cohort 2 and part of Cohort 1: to assess respiratory syncytial virus (RSV) neutralizing antibody levels of the regimens containing RSV pre-fusion (preF) protein compared to the one-dose adenovirus serotype 26 respiratory syncytial virus pre-fusion (Ad26.RSV.preF) regimen.Cohort 3: to assess the safety and reactogenicity of the selected regimen and a booster at Month 12 and/or Month 24.