Safety and efficacy of an rAd26 and rAd5 vector-based heterologous prime-boost COVID-19 vaccine: an interim analysis of a randomised controlled phase 3 trial in Russia.

Abstract (PubMed)

A heterologous recombinant adenovirus (rAd)-based vaccine, Gam-COVID-Vac (Sputnik V), showed a good safety profile and induced strong humoral and cellular immune responses in phase 1/2 trials. We report preliminary results on the efficacy and safety of Gam-COVID-Vac from an interim analysis of this phase 3 trial. Randomised, double-blind, placebo-controlled, phase 3 trial at 25 hospitals and polyclinics in Moscow. Participants ≥18 years, negative SARS-CoV-2 PCR/IgG/IgM, randomised 3:1 (vaccine:placebo). Vaccine administered intramuscularly in prime-boost (rAd26-S then rAd5-S, 21-day interval). Primary endpoint: COVID-19 confirmed from day 21 after first dose. 21,977 enrolled, 19,866 received two doses. Efficacy 91.6% (95% CI 85.6–95.2); 16 cases (0.1%) vaccine vs 62 (1.3%) placebo. Serious adverse events: 0.3% vaccine vs 0.4% placebo. Four deaths (3 vaccine, 1 placebo), none attributed to vaccine.