This is a randomized, double-blind, parallel-controlled, equivalence trial, for evaluation of safety and immunogenicity, and batch-to-batch consistency of a recombinant adenovirus type-5-vectored Covid-19 vaccine Convidecia in one shot schedule in Chinese healthy adults aged 18 years and above. In total 1050 healthy adults will be recruited in this study. Subjects in both cohort will be randomized stratified into two cohort by age(18~59 years and≥60 years) in a 1:1:1 ratio to receive one of three consecutive batches of Convidecia. The primary objective is to test the equivalence of the immune responses to three consecutive manufacturing lots of Convidecia in healthy adults. The secondary objectives were to evaluate the immunogenicity and safety of Convidecia for each lot and the pooled data of three lots)

Inclusion Criteria:

1. healthy participants aged 18 years and above who have not received COVID-19 vaccine.
2. The subjects can provide with informed consent and sign informed consent form (ICF).

4. The subjects are able to and willing to comply with the requirements of the clinical trial program and could complete the follow-up of the study.

5. Axillary temperature ≤ 37.0℃. 6. negative IgM and IgG against SARS-CoV-2 7. with BMI between18.5 to 30.0 8. No history of epidemiological contact with COVID-2019 9. have not been to medium or high risk areas in the past 21 days and have no history of departure.

10. be determined to be healthy by medical history, physical examination and clinical examination and meet the requirements for immunization of this product.

Exclusion criteria:

1. Medical history or family history of convulsion, epilepsy, encephalopathy and psychosis.
2. Allergic to any component of the research vaccines, or a history of hypersensitivity or serious reactions to vaccination.
3. Women with positive urine pregnancy test, pregnant or breast-feeding, or have a pregnancy plan in this study.
4. Suffering from acute febrile disease, infectious disease, or SARS infection history
5. Serious cardiovascular disease, such as arrhythmia, conduction block, myocardial infarction, severe hypertension, which cannot be controlled by medication (systolic blood pressure ≥180mmHg, diastolic blood pressure ≥110mmHg)
6. Have severe chronic diseases or unstable condition ( Grade 3 or higher as defined in the guidelines for the classification of adverse events in clinical trials for prophylactic vaccines), Such as diabetes, thyroid disease and so on.
7. Congenital or acquired angioedema / neuroedema.
8. had urticaria one year before this vaccination.
9. Asplenia or functional asplenia.
10. Thrombocytopenia or other clotting disorder (this may contraindicate intramuscular injection).
11. Faintng during acupuncture treatment
12. Received immunosuppressant therapy, antiallergic therapy, cytotoxic therapy, high dose inhaled corticosteroid over the past 6 months (excluding corticosteroid spray for allergic rhinitis, surface corticosteroid for acute non-complicated dermatitis, and corticosteroid with dose less than 20mg/ day)
13. Received blood products within 4 months before vaccination.
14. Received other investigational drugs within 1 month prior to receiving the investigational vaccines.
15. Received other live attenuated vaccines within 1 month prior to receiving the investigational vaccines.
16. Received subunit or inactivated vaccine within 14 days prior to receiving investigational vaccine.
17. Be receiving anti-tuberculosis treatment
18. Have the history of SARS-CoV-2 infection or COVID-19
19. Any medical, psychological, social or other conditions that, in the investigator's judgment, are inconsistent with the study protocol or affect the subjects' informed consent

Participants and investigators will be kept blinded.