A Single-Center, Randomized, Blind, Phase II Clinical Trial to Evaluate the Safety and Immunogenicity of the Adenovirus Type 5 Vector Based Ebola Virus Disease Vaccine (Ad5-EBOV) in Healthy Adults Aged Between 18 and 50 years in Sierra Leone.

Inclusion Criteria:

• Aged between 18 and 50 years
• Able to understand the content of informed consent and signed the informed consent
• Able and willing to complete all the secluded study process during the whole study follow-up period (about 6 months).
• Negative in HIV diagnostic blood test on day of enrollment
• Axillary temperature ≤37.0°C on the day of enrollment
• Non-pregnant females with a negative result in the urine pregnancy test on day of enrollment
• General good health as established by medical history and physical examination.

Exclusion Criteria:

• Infected by Ebola virus (inquiry)
• Vaccination with other Ebola vaccine (inquiry)
• HIV infection or other serious immunodeficiency disease (inquiry)
• Allergic history of any vaccination or drugs, or allergic to any ingredient of the Ad5-EBOV, such as mannitol
• Family history of brain or mental disease
• Woman who is pregnant or breast-feeding
• Any acute fever disease or infections in last 7 days
• Major congenital defects or not well-controlled chronic illness
• Asplenia or functional asplenia
• Platelet disorder or other bleeding disorder
• Faint at the sight of blood or needles.
• Prior administration of immunodepressant or corticosteroids, antianaphylaxis treatment, cytotoxic treatment in last 6 months
• Prior administration of other research medicines in last 1 month
• Prior administration of attenuated vaccine(s) in the last one month
• Prior administration of inactivated vaccine(s) in the last 14 days
• Any condition that in the opinion of the investigators may interfere with the participants' compliance or evaluation of study objectives