Interim phase-3 trial results show Sputnik V vaccine has 91.6% efficacy

Results of an interim analysis of phase-3 trial of Russia’s Sputnik V vaccine show the vaccine is safe and has 91.6% efficacy. The efficacy against severe disease increased to 100% after 21 days. Although the study was not designed to assess the efficacy of a single dose regimen, the researchers were able to observe a possible partial protective effect of a single dose.

Results of an interim analysis of phase-3 trial of Russia’s Sputnik V vaccine shows the vaccine is safe and has 91.6% efficacy. The efficacy against severe disease increased to 100% after 21 days.

The efficacy was 91.6% after the first dose. Although the study was not designed to assess the efficacy of a single dose regimen, the researchers were able to observe a possible partial protective effect of a single dose. The results were published in The Lancet.

The liquid form of the vaccine that requires storage at minus 18 degree C was studied. Storage at 2-8 degree C, a favourable temperature profile for global distribution, has been approved by the Ministry of Health of the Russian Federation. Dr. Reddy’s Lab in Hyderabad is testing the vaccine in India.

The phase-3 trial carried between September 7 and November 24, 2020 in about 20,000 participants found that the vaccine was safe. The phase-3 trial was carried out in Moscow at 25 sites accredited by the Health Ministry for the conduct of clinical research. The time-point for the interim analysis was when 78 COVID-19 cases were reported in participants after receiving the second dose.  

Of the about 20,000 participants, about 15,000 received the vaccine while over 4,900 got the placebo. The primary outcome was the proportion of participants with COVID-19 from day 21 after receiving the first dose. On day 21 after the first dose, 16 participants in the vaccine arm and 62 in the placebo group were confirmed to have COVID-19. This translates to 91.6% vaccine efficacy. The efficacy against severe disease increased to 100% after the second dose was administered on day 21.

Safety of the vaccine

Serious adverse events were seen in both arms — 45 in the vaccine arm and 23 in the placebo group — but “none were considered associated with vaccination”, as confirmed by the independent data monitoring committee. Four deaths were also reported during the study — three in the vaccine arm and one in the placebo group — but “none of the deaths were considered related to the vaccine”, the paper reports.

The incidence rate in the two groups showed that the immunity required to prevent disease arose within 18 days of the first dose. The protection was seen in all age groups, including those older than 60 years. The vaccine efficacy in those older than 60 years did not differ significantly from the 18-60 years group, the paper says.

The 91.6% efficacy, based on the numbers of confirmed COVID-19 cases after the first dose of vaccine, suggests lessening of disease severity after the first dose. “This is particularly encouraging for current dose-sparing strategies,” says a Comment piece published alongside the paper.

Results silence the critics

“The development of the Sputnik V vaccine has been criticised for unseemly haste, corner cutting, and an absence of transparency. But the outcome reported here is clear and the scientific principle of vaccination is demonstrated, which means another vaccine can now join the fight to reduce the incidence of COVID-19,” says the Comment piece by Ian Jones of the University of Reading and Polly Roy of the London School of Hygiene and Tropical Medicine.

The Sputnik V vaccine uses an approach slightly different from the one used by AstraZeneca. While AstraZeneca uses the same the adenovirus serotype for the first and second dose to ferry the genetic material into the cells, the Sputnik V vaccine uses two different adenovirus serotypes — adenovirus 26 (Ad26) for the first dose and adenovirus 5 (Ad5) for the second dose. Pre-existing immunity to adenovirus can reduce the efficacy of the vaccine. Using two varying serotypes of adenovirus, which are given 21 days apart, is intended to overcome any pre-existing adenovirus immunity in the population.

Published in The Hindu on February 2, 2021