It is the latest vaccine to show encouraging preliminary results (Picture: Getty)
Russia’s Sputnik V vaccine is more than 91% effective against symptomatic coronavirus, according to interim results.
No serious adverse events were linked to the jab and most reported reactions were mild, including flu-like symptoms, pain at the injection site and weakness or low energy.
The phase three trial, involving 20,000 participants, found Gam-COVID-Vac to offer 91.6% efficacy, in people aged over 18, including older adults.
The study, published in The Lancet, saw three quarters of participants receive the two-dose vaccine and a quarter given a placebo. Those given the jab had ‘robust’ antibody and T-cell responses to the virus.
The jab provides two ‘adenovirus vectors’ which have been modified in line with the virus’ spike protein
The vectors are also weakened so that they cannot replicate in human cells or cause disease.
In the trial, participants were given a dose of one vector followed by a booster dose of a different one 21 days later.
Vials of the Russian jabs (Picture: AFP)
According to the researchers, using a different vector in the booster vaccination may help create a more powerful immune response, compared with using the same vector twice.
They suggest this is because it minimises the risk of the immune system developing resistance to the initial vector.
Dr Inna V Dolzhikova, co-lead author, from the Gamaleya National Research Centre for Epidemiology and Microbiology in Russia, said: ‘Our interim analysis of the randomised, controlled, phase 3 trial of Gam-COVID-Vac in Russia has shown high efficacy, immunogenicity, and a good tolerability profile in participants aged 18 years or older.’
Between September 7 and November 24 last year, a total of 21,977 adults were randomly assigned to receive the vaccine (16,501) or placebo (5,476).
In the vaccine group 14,964 participants, and 4,902 in the placebo group, received two doses of the vaccine or placebo and were included in the primary interim efficacy analysis reported on Tuesday.
A medical worker and a patient before getting the Sputnik V vaccine (Picture: Getty Images)
From 21 days after receiving the first dose – the day of the second dose, 16 cases of symptomatic Covid-19 were confirmed in the vaccine group, and 62 cases in the placebo group – equivalent to an efficacy of 91.6%.
Researchers say the vaccine induced a robust antibody response and T-cell response with data from 342 and 44 participants, respectively.
Six of the 342 participants did not mount an immune response following vaccination, possibly due to older age or individual characteristics, researchers said.
The authors note that because Covid-19 cases were detected only when participants self-reported symptoms, followed by a test, the efficacy analysis only includes symptomatic cases of the virus.
They say further research is needed to understand the efficacy of the vaccine on asymptomatic Covid-19, and on transmission.
The median follow-up was 48 days from the first dose, so researchers warned that they cannot assess the length of protection provided.
Four deaths were recorded during the trial – three in the vaccine group, and one in the placebo group but none associated with the vaccine.
In the vaccine group, one death was associated with a fracture, and two had underlying conditions and developed symptoms of the virus four to five days after the first dose of the vaccine.
Both participants were deemed to have already been infected before inclusion in the trial.
In the placebo group, the death was associated with a stroke.
The trial included 2,144 participants more than 60 years old, and vaccine efficacy was 91.8% in this group.
The vaccine was well tolerated and safety data from 1,369 of these older adults found that the most common adverse events were flu-like symptoms and local reaction.
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