A Russian coronavirus bite is 91.6% effective with no adverse side effects.
Phase three in the Gam-COVID-Vac (Sputnik V) study suggests that two-dose regimen of the vaccine is 91.6% effective and reports only mild symptoms – including flu-like symptoms and pain at the injection site.
The preliminary results, published in The Lancet, are based on an analysis of data from nearly 20,000 participants, three quarters of whom received the vaccine and a quarter received a placebo.
The sting is a two-part vaccine that contains two adenovirus vectors – recombinant human adenovirus type 26 (rAd26-S) and recombinant human adenovirus type 5 (rAd5-S) – that have been modified to contain the SARS-CoV-2 spike protein to express.
The adenoviruses are also weakened so that they cannot multiply in human cells and cannot cause disease.
In the study, participants received a dose of rAd26-S followed by a booster dose of rAd5-S 21 days later.
According to the researchers, using a different adenovirus vector for the booster may help create a stronger immune response than using the same vector twice.
They suggest this because it minimizes the risk of the immune system developing resistance to the original vector.
Dr. Inna V Dolzhikova, co-lead author of the National Research Center for Epidemiology and Microbiology in Gamaleya, Russia, said: “Our interim analysis of the randomized, controlled phase 3 study of Gam-COVID-Vac in Russia has shown high efficacy, immunogenicity and a good tolerance profile for participants aged 18 and over. “
Between September 7 and November 24 last year, a total of 21,977 adults were randomly selected to receive the vaccine (16,501) or the placebo (5,476).
14,964 participants in the vaccine group and 4,902 in the placebo group received two doses of the vaccine or placebo and were included in the primary interactions analysis reported Tuesday.
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 – an effectiveness of 91.6%.
Researchers say the vaccine induced a robust antibody response and a T cell response with data from 342 and 44 participants, respectively.
Six of the 342 participants showed no immune response after vaccination, possibly due to older age or individual characteristics.
The authors note that the effectiveness analysis only includes symptomatic cases of the virus, as Covid-19 cases were only discovered when participants reported symptoms themselves, followed by a test.
They say more research is needed to understand the vaccine’s effectiveness on asymptomatic Covid-19 and transmission.
The median follow-up was 48 days from the first dose, so that the entire duration of protection cannot be assessed in the study.
Four deaths were recorded during the study – three in the vaccine group and one in the placebo group.
In the vaccine group, one death was associated with a fracture, and two had underlying illnesses and developed symptoms of the virus four to five days after the first vaccine dose.
Both participants were infected prior to enrollment in the study.
In the placebo group, death was associated with a stroke. None of the deaths were considered to be related to vaccination.
The study included 2,144 participants who were older than 60 years and the vaccine effectiveness in this group was 91.8%.
The vaccine was well tolerated and safety data from 1,369 of these older adults indicated that the most common adverse events were flu-like symptoms and local reactions.