Russian vaccine is 91.6% effective against symptomatic Covid - how it works

By Claire Schofield
Published 2nd Feb 2021, 14:42 BST
Updated 2nd Feb 2021, 15:20 BST
The vaccine is 91.6 per cent effective against symptomatic Covid-19 (Photo: Getty Images)The vaccine is 91.6 per cent effective against symptomatic Covid-19 (Photo: Getty Images)
The vaccine is 91.6 per cent effective against symptomatic Covid-19 (Photo: Getty Images)

Russia’s vaccine is 91.6 per cent effective against symptomatic Covid-19, interim trial results show.

The preliminary findings, published in The Lancet, are based on analysis of data from nearly 20,000 participants, three quarters of whom were given the vaccine. One quarter received a placebo.

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Two dose vaccine

Interim data from the phase three trial of the vaccine, Gam-COVID-Vac, or Sputnik V, suggests that two doses of the jab will offer 91.6 per cent efficacy.

The vaccine includes two adenovirus vectors - recombinant human adenovirus type 26 (rAd26-S) and recombinant human adenovirus type 5 (rAd5-S) - which have been modified to express the SARS-CoV-2 spike protein. The adenoviruses are also weakened so that they cannot replicate in human cells and cause disease.

In the trial, participants were given one dose of rAd26-S, followed by a booster dose of rAd5-S 21 days later.

Using a different adenovirus vector for the booster vaccination may help to create a more powerful immune response, compared with using the same vector twice, according to the researchers. They suggest this is because it minimises the risk of the immune system developing resistance to the initial vector.