A Phase III Clinical Trial of the Immunogenicity and Safety of the Gam-COVID-Vac Vaccine Against COVID-19 in the UAE

Inclusion Criteria: 1. Agree to sign the study informed consent form (ICF) before performing any study-specific procedure. 2. Adults, i.e., ≥ 18 years old. 3. Negative HIV, hepatitis B, hepatitis C, and syphilis test results 4. Negative IgM and IgG SARS CoV2 antibodies enzyme immunoassay test result. 5. Negative COVID-19 RT-PCR test result at the screening visit. 6. No COVID-19 in medical history. 7. Subjects to confirm they had no contact with COVID-19 persons within at least 14 days before the screening visit. 8. Consent for using effective methods of contraception during the entire trial1 9. A negative urine pregnancy test at the screening visit (for child-bearing age women). 10. Negative alcohol test at the screening visit. 11. No evidence of vaccine-induced reactions or complications after receiving immunobiological products in medical history. 12. No acute infectious and/or respiratory diseases within at least 14 days before the enrollment. Exclusion criteria: 1. Any vaccination/immunization within 30 days before the enrollment. 2. History of COVID-19. 3. Positive SARS-CoV-2 screening result obtained by PCR (at screening). 4. Test results for IgM and IgG antibodies to SARS-CoV-2 is positive. 5. Administration of steroids (except hormonal contraceptives) and/or immunoglobulins or other blood products therapy not finished 30 days before the enrollment. 6. Pregnancy or breast-feeding. 7. Acute coronary syndrome or stroke suffered less than one year before the enrollment. 8. Tuberculosis, chronic systemic infections in medical history. 9. Drug allergy (anaphylactic shock, Quincke's edema, polymorphic exudative eczema, atopy, serum disease), hypersensitivity or allergic reaction to immunobiological products, known allergic reactions to study vaccine components, acute exacerbation of allergic diseases on the enrollment day. 10. Known allergic reactions to vaccination 11. History of asthma 12. Neoplasms in medical history. 13. Major operations in the past 12 months before study vaccine administration. This will include but not limited to; major organs transplant, bone marrow donation, etc. 14. Splenectomy in the past medical history 15. Neutropenia (absolute neutrophil count \<1,000 mm3), agranulocytosis, significant blood loss, severe anemia (hemoglobin \<80 g/L), immunodeficiency in the medical history within 6 months before the enrollment. 16. Any family member with immunodeficiency, cancer, or transplantation 17. The active form of a disease caused by the human immunodeficiency virus, syphilis, hepatitis B, or C. 18. Subjects with diabetes, heart disease, chronic kidney disease, or dialysis 19. Subjects with latent tuberculosis infection 20. Anorexia, protein deficiency of any origin. 21. Subjects with any metabolic diseases 22. Tattoos or scars at the injection site (deltoid muscle area), which in the medical opinion of the investigator does not allow assessing the local response to the study vaccine/placebo administration. 23. Alcohol or drug addiction in medical history. 24. Participation in any other interventional clinical trial within the previous 90 days (from the administration of the Vaccine). 25. Any other condition that the study physician considers as a barrier to the trial completion as per the protocol. 26. Healthcare workers