The Phase 3 trial will include 2,000 volunteers over the age of 18. After screening, they will be randomised (3:1) into two groups - a reference group of 500 volunteers who will receive the placebo and a study group of 1,500 volunteers who will receive the combined Gam-COVID-Vac vaccine against SARS-induced coronavirus infection-СoV-2oV-2.

The trial subjects will be randomized into five age strata: 18-30, 31-40, 41-50, 51-60 and 60+ years. Each subject will participate in the trial for 180±14 days after the first dose of the study drug/placebo and will have one screening visit and five on-site visits to the study physician during the said period.

The study drug/placebo will be administered intramuscularly during vaccination visits 1 and 2 (day 1 and day 21±2). Follow-up visits Nos. 3, 4, 5 will be conducted on days 28±2, 42±2 and 180±14, respectively. Blood samples will be taken from certain subjects during the following visits to assess the immunogenicity parameters on days 1, 42±2 and 180±14.

During observation visits, vital indicators will be assessed on all trial subjects and changes in the subjects' condition and well-being will be recorded, observational visits may be remote, using telemedicine (TM) technologies. Additionally, the trial subjects will be able to have remote consultations with the study physician through the TM. Data from trial subjects will be collected through electronic case report forms.