Safety, Tolerability, and Immunogenicity of the Ebola Chimpanzee Adenovirus Vector Vaccine (cAd3-EBO), VRC-EBOADC069-00-VP, in Healthy Adults

Background: \- Ebola virus causes an infection known as Ebola virus disease (EVD). This it is generally a severe disease which can also lead to death. The 2014 outbreak of EVD in West Africa is the largest ever. Researchers want to develop a vaccine to prevent Ebola infection. It is impossible for someone to get an Ebola infection from this vaccine. Objectives: \- To see if an Ebola vaccine is safe and to study immune responses to it. Eligibility: \- Healthy adults ages 18-65. Design: * Participants will be screened through a separate protocol. * Participants will receive the vaccine injection by needle and syringe into an upper arm muscle. - Participants will stay at the clinic for 3 hours after the injection. * About 2 days later, participants must speak with clinic staff about how they are doing. * Every day for 7 days after the injection, participants will record their temperature and symptoms and look at the injection site. They will get a thermometer and a ruler to measure any redness or swelling. They will report any side effects. * In the first 2 months in the study, participants will have at least 6 clinic visits and 1 phone call. They will have at least 3 other visits over the next 9 months. * At each visit, participants will be checked for health changes or problems since their last visit. They will be asked how they feel and if they have taken any medicine. Blood will be drawn at most visits. Urine samples may be collected.