Clinical Study of the Safety and Immunogenicity of a Recombinant Viral Vector AAV5 (Adeno-Associated Virus Type 5 )-RBD (Receptor Binding Domain)-S Vaccine for the Prevention of Coronavirus Infection (COVID-19)

A randomized, double-blind, placebo-controlled, adaptive, seamless phase I / II clinical study of the safety and immunogenicity of a recombinant viral vector AAV5-RBD-S vaccine for the prevention of coronavirus infection (COVID-19)

The study will be carried out in 2 stages. Stage 1 aims to assess the safety and immunogenicity of different doses of BCD-250 in subjects without a history of COVID-19 infection to choose the optimal dose for further investigation.

Stage 2 aims to assess the immunogenicity and safety of the chosen on stage 1 optimal BCD-250 dose compared to placebo in subjects with and without the history of COVID-19 infection.

Eligibility Criteria:
Inclusion Criteria:

* Signed informed consent form
* Ability to comply with the study procedures based on the Investigator's assessment
* Males and females aged 18-60 years, inclusive, at the date of consent.
* Negative pregnancy test (for females of childbearing potential)
* Patients of childbearing potential and their partners with preserved reproductive function must agree to use reliable contraceptive methods starting from the time of informed consent for 3 months after Visit 1. This requirement does not apply to patients and their partners who underwent surgical sterilization. Reliable contraceptive methods include one barrier method in combination with one of the following: spermicides, intrauterine device/oral contraceptives.
* Cohort 1 only. Negative test for SARS-CoV-2 IgM and IgG at screening
* Cohort 2 only. Negative test for SARS-CoV-2 IgM at screening
* Cohort 2 only. Confirmed by SARS-CoV-2 RNA test, history of COVID-19 with documented recovery at least 4 month prior consent date.

Exclusion Criteria:

* Positive / uncertain test for SARS-CoV-2 RNA at screening
* Cohort 1 only. Documented history of COVID-19.
* Changes on chest X-ray suggestive for pneumonia or other lung diseases at screening, excluding clinically non-significant changes in subjects with COVID-19 history on investigator's opinion.
* Prior administration of SARS-CoV-2 or other coronavirus vaccine or planning of receiving SARS-CoV-2 or other coronavirus vaccine during the study participation.
* Known contact with SARS-CoV-2 infected person or person with known contact with SARS-CoV-2 infected person, within 14 days prior to consent date.
* Any acute infectious or non-infectious disease, including convalescence period, less than 4 weeks since clinical recovery
* Positive HIV, HBV, HCV or Syphilis tests
* History of splenectomy
* History of severe allergic reactions
* History of allergic or postvaccinal reactions (anaphylactic shock, fever of 40°C or more, fainting, non-febrile convulsions etc.) after vaccine administration
* Suspicious hypersensitivity or history of hypersensitivity to any component of investigational product
* Participation in other clinical studies within 90 days prior to consent date, excluding screen failures or discontinued prior to the first investigational product administration.