Russian Sputnik vaccine reports 91% efficacy at 21 days after the first dose

Simon Collins, HIV i-Base

On 2 February 2021, early interim phase 3 efficacy result from the Russian recombinant adenovirus-based vaccine, Gam-COVID-Vac (Sputnik V) were published in the Lancet. [1]

This double-blind, placebo-controlled study randomised 21,977 adults between 7 September and 24 November 2020 to either the vaccine (n=16 501) or placebo (n=5476) groups. [2]

The vaccine was developed by the Gamaleya Research Institute in Moscow and the study was run at 25 hospitals in Moscow.  The study involves a prime boost vaccination schedule using two vaccinations, three weeks apart. However, the primary endpoint in this interim analysis – called to determine whether sufficient early efficacy could limit the need for further use of a placebo arm during a growing COVID-19 crisis – was confirmed COVID-19 infection 21 days after the first vaccine (ie when the second vaccine was given). 

Baseline characteristics included 61% male, 98% Caucasian and 35% were >50 years old.

Based on 16 (0.1%) vs 62 (1.3%) confirmed cases in the active vs placebo groups, the paper reported 91.6% efficacy (95% CI: 85.6 to 95.2).

Tolerability was good with most adverse events reported as grade 1. None of the more erious events (45 vs 23; 0.3 vs 0.4%) were judged to be vaccine related.


  1. Logunov DY et al. 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. Lancet 397(10275)p671-681. DOI: 10.1016/S0140-6736(21)00234-8. (20 February 2021).
  2. Clinical trial of efficacy, safety, and immunogenicity of Gam-COVID-Vac vaccine against COVID-19 (RESIST).

Links to other websites are current at date of posting but not maintained.