Screening Period = up to 7 days All screening procedures must be executed within the shortest possible time frame before the scheduled date for Visit 1 (drug administration). The laboratory and instrumental examination data obtained within 14 days before the screening will be recorded as the screening data.

The trial will include 110 volunteers that will be administered the study drug. Outpatient observation will be done over the course of 4 visits: on day 10, 28, and 42 following drug administration Along with that, the study will be continued in accordance with the Protocol, accompanied by all the prescribed procedures and visits up to 180 days of observation.

Visit No. 0 (outpatient): screening Visit No. 1 (outpatient): vaccination Visits No. 2, 3, 4, 5, and 8: follow-up on days 10, 28, 42, 90, and180 after vaccination.

On days 120 and 150, visits 6 and 7 will be accomplished by telephone contact / telemedicine conference or, if necessary, in the form of an in-person visit.

Any volunteer who received a dose of the study drug will be registered as a trial participant, and his/her data will be used to help assess the drug's safety and tolerability.

Results

On November 2, 2021, The Lancet Europe published the results of this clinical trial.

Most of the solicited adverse reactions were mild (66·4% from all vaccinees), few were moderate (5·5%). No serious adverse events were detected. Assessment of Anti-RBD-SARS-CoV-2 antibodies revealed a group with pre-existing immunity to SARS-CoV-2. Upon this finding we separated all safety and immunogenicity data based on pre-existing immunity to SARS-CoV-2. There were notable differences in the vaccine effects on immunogenicity by the groups. Vaccination of seropositive (N=14) volunteers rapidly boosted RBD-specific IgGs from reciprocal geometric mean titer (​GMT) 594·4 at a baseline up to 26899 comparing to 29·09 in seronegative group (N=96) by day 10. By day 42 seroconversion rate reached 100% (93/93) in seronegative group with GMT 1648. At the same time, in the seropositive group, seroconversion rate by day 42 was 92·9% (13/14) with GMT 19986. Analysis of neutralizing antibodies to SARS-CoV-2 showed 81·7% (76/93) and 92·9% (13/14) seroconversion rates by day 42 with median reciprocal GMT 15·18 and 579·7 in the seronegative and seropositive groups, respectively. Antigen-specific T cell proliferation, formation of IFNy-producing cells, and IFNy secretion were observed in 96·7% (26/27), 96% (24/25), and 96% (24/25) of the seronegative group respectively and in 100% (3/3), 100% (5/5), and 100% (5/5) of the seropositive vaccinees, respectively.

Conclusion

The single-dose rAd26 vector-based COVID-19 vaccine “Sputnik Light” has a good safety profile and induces a strong humoral and cellular immune responses both in seronegative and seropositive participants.