This first-in-human study consists of 2 parts: 1) The main study, which is randomized, placebo-controlled, observer-blind; 2) A sub-study, which is open-label, uncontrolled, non-randomized study evaluating the safety, tolerability, and immunogenicity of MVA-BN-Filo and Ad26.ZEBOV administered in different sequences and schedules to healthy adult participants. The study consists of a Screening period (up to 28 days in the main study and up to 56 days in the sub-study), a vaccination period in which participants will be vaccinated at baseline (Day 1) followed by a boost on Day 15, 29 or 57, and a post-boost follow-up until all participants have had their 21-day post-boost visit (Day 36, 50 or Day 78). The total duration of the study will be about 1 year for participants who received vaccine and about 3 months for participants who received placebo. Safety will be monitored during the study.