A Study to Assess the Safety and Immunogenicity of Heterologous Prime-Boost Ebola Vaccine Regimens in Healthy Participants

Inclusion Criteria: * Must be healthy on the basis of physical examination, medical history, and the investigator's clinical judgment * Women of childbearing potential must have a negative serum beta-human chorionic gonadotropin pregnancy test at screening, a negative urine pregnancy test immediately prior to each study vaccine administration, and practice adequate birth control measures from 28 days before the prime vaccination until at least 3 months after the boost vaccination as specified in the study protocol. If not heterosexually active at screening, must agree to practice adequate birth control measures if they become heterosexually active during their participation in the study (from screening onwards until at least 3 months after the boost vaccination). * Must be available and willing to participate for the duration of the study visits and follow-up, provide verifiable identification, and have a means to be contacted Exclusion Criteria: * Has been vaccinated with a candidate Ebola vaccine * Has been diagnosed with Ebola disease or exposed to Ebola including travel to West Africa in the last 12 months. West Africa includes but is not limited to the countries of Guinea, Liberia, Mali, and Sierra Leone. Participants who anticipate traveling to epidemic Ebola areas before the start of the long-term follow-up period will also be excluded. During the long-term follow-up period, travel to epidemic Ebola areas is allowed but during this period sampling can only take place if participant has returned at least 1 month from the epidemic Ebola area to ensure the samples are not carrying the Ebola-virus * Has received any Ad26- or MVA-based candidate vaccine in the past * Known allergy or history of anaphylaxis or other serious adverse reactions to vaccines or vaccine products (including any of the constituents of the study vaccines), including known allergy to egg or aminoglycosides * A woman who is pregnant or breast-feeding, or planning to become pregnant while enrolled in the study or within 3 months after the boost vaccination * History of diabetes mellitus type 1 or type 2, including cases controlled with diet alone; thyroidectomy, or thyroid disease requiring medication during the last 12 months; uncontrolled hypertension as defined in the study protocol; or, major psychiatric illness and/or substance abuse problems during the past 12 months that in the opinion of the investigator would preclude participation