A Phase II Clinical Trial to Evaluate the Recombinant Vaccine for COVID-19 (Adenovirus Vector)

Inclusion Criteria: * Aged between 18 and 60 years. * Able to understand the content of informed consent and willing to sign the informed consent * Able and willing to complete all the secluded study process during the whole 6 months study follow-up period. * Negative in HIV diagnostic test. * Negative in serum antibodies (IgG and IgM) screening of COVID-19. * Axillary temperature ≤37.0°C. * The BMI index is 18.5-30.0. * General good health as established by medical history and physical examination. Exclusion Criteria: * Family history of seizure, epilepsy, brain or mental disease * Subject allergic to any component of the investigational vaccine, or a more severe allergic reaction and history of allergies in the past. * Woman who is pregnant, breast-feeding or positive in β-HCG (human chorionic gonadotropin) pregnancy test (urine) on day of enrollment, or become pregnant during the next 6 months * Any acute fever disease or infections. * History of SARS * Major congenital defects or not well-controlled chronic illness, such as asthma, diabetes, or thyroid disease. * Serious cardiovascular diseases, such as arrhythmia, conduction block, myocardial infarction, severe hypertension without controllable drugs, etc. * Hereditary angioneurotic edema or acquired angioneurotic edema * Urticaria in last one year * No spleen or functional spleen. * Platelet disorder or other bleeding disorder may cause injection contraindication * Faint at the sight of needles. * Prior administration of immunodepressant or corticosteroids, antianaphylaxis treatment, cytotoxic treatment in last 6 months. * Prior administration of blood products in last 4 months * Prior administration of other research medicines in last 1 month * Prior administration of attenuated vaccine in last 1 month * Prior administration of inactivated vaccine in last 14 days * Current anti-tuberculosis prophylaxis or therapy * According to the judgement of investigator,various medical, psychological, social or other conditions, those could affect the subjects to sign informed consent.