Study early terminated based on the sponsor(manufacture)'s decision

The immunogenicity and safety profiles of AdCLD-CoV19-1 (5.0×10^10 VP/dose) will be assessed for 1-dose or 2-dose regimen in SARS-CoV-2 seronegative healthy adults.

Inclusion Criteria:

1. Healthy individual aged 19 years and above at consent.
2. Individual willing to provide written informed consent to participate study voluntarily.
3. Individuals who can be followed up during the study period and can comply with the study requirements.
4. Individual who agrees not to donate blood during the study participation
5. Females of childbearing potential with negative serum or urinary pregnancy test on the day of screening.
6. Females of childbearing potential who are using an effective birth control method for at least 4 weeks before the screening and during the study participation.

Exclusion Criteria:

1. Prior SARS-CoV-2 infection confirmed by a rapid antibody kit at screening.

2. History of receiving any vaccine (licensed or investigational) for SARS-CoV-2.

3. History of SARS-CoV-1 or MERS vaccination and treatment.

4. Individual determined to be clinically significantly abnormal by the screening outcome based on medical history, physical examination, laboratory evaluations (positive serological tests for Hepatitis B surface antigen (HBsAg), Hepatitis C antibody, and Human Immunodeficiency Virus (HIV) antibody), electrocardiogram (ECG) and Chest X-ray, and the clinical judgment of the investigator.

5. Individual who has received other vaccines from 4 weeks prior to the first dose of test vaccination or planned to receive any vaccine within 4 weeks of the last dose of the study vaccine.

6. Febrile illness (tympanic temperature ≥ 38°C) or acute illness with any clinically significant, respiratory symptoms (e.g., sore throat, cough, sputum) within 3 days prior to the study vaccination.

7. Known history or allergy to study vaccine components and/or excipients or other medications, or any other allergies deemed by the investigator to increase the risk of an adverse event if they were to participate in the trial (e.g., Guillain-Barre Syndrome).

8. Individual with major congenital abnormalities, which in the opinion of investigator may affect the participant's participation in the study.

9. Chronic use of systemic steroids (>10 mg/day prednisone equivalent for periods exceeding 14 days), cytotoxic or other immunosuppressive drugs within the past 6 weeks.

10. Any abnormality or chronic disease which in the opinion of the investigator might be detrimental to the safety of the participant and interfere with the assessment of the study objectives.

    ① Respiratory diseases: Asthma, Chronic Obstructive Lung Disease (COPD), active or latent tuberculosis which require medication, etc.

    ② Serious cardiovascular diseases: Congestive heart failure, coronary artery disease, myocardial infarction, uncontrolled hypertension, myocarditis, pericarditis, etc.

    ③ Neurologic diseases: Epilepsy, seizure within 3 years, migraine, stroke, encephalopathy, Guillain-Barre Syndrome, encephalomyelitis, acute transverse myelitis, etc.

    ④ Malignant cancer diagnosed within the past 5 years (skin basal cell and squamous cell carcinoma are excluded).

    ⑤ Immune function disorders, including auto-immune diseases and immunodeficiency diseases (known HIV infection or other immune function disorders)

    ⑥ Other hepatobiliary, renal, endocrine, urinary tract, muscular skeletal diseases which the investigator considers clinically significant

11. Individual with hereditary or idiopathic angioneurotic edema

12. Individuals with behavioral or cognitive impairment or psychiatric disease or neural disorders that, in the opinion of the investigator, could interfere with the participant's ability to participate in the trial.

13. Individual with splenectomy and transplantation (including solid organ and bone marrow).

14. Individual with past history of thrombocytopenia and/or thrombosis, myocarditis or pericarditis or any other significant cardiac condition.

15. Individual with a known bleeding diathesis, or any condition that may be associated with a prolonged bleeding time resulting in contraindication for IM injections/blood extractions (Those who receive low dose aspirin (less than 100mg/day) are not excluded).

16. Receipt of immunoglobulin or blood-derived products in the past 12 weeks or plan to receive during the study period.

17. Body mass index (BMI) ≥ 30 kg/m2.

18. As per Investigator's medical judgement, an individual could be excluded from the study in spite of meeting all inclusion/exclusion criteria mentioned above.

19. Any female participant who is lactating*, pregnant or planning for pregnancy** during the course of study period.

20. Individual concomitantly enrolled or scheduled to be enrolled in another trial.

21. Individual who is research staff involved with the clinical study or family/household members of research staff.

The study is designed as observer-blinded.