The preliminary findings were published Tuesday in The Lancet and are based on data collected from 19,866 participants, of whom approximately three-quarters (14,964) received two doses of the vaccine and a quarter (4,902) received a placebo.
Sixteen cases of symptomatic Covid-19 were confirmed in the vaccine group 21 days after the participants received the first vaccine dose. Sixty-two cases were found in the placebo group – corresponding to an efficacy of 91.6%.
The trial included 2,144 people over 60 years of age and a sub-analysis performed on this group revealed that the vaccine was well tolerated and had a comparable efficacy of 91.8%.
The team also analyzed the efficacy of the vaccine against severe and moderate Covid-19 disease and 21 days after the first dose, no serious or moderate cases were reported in the vaccinated group, while 20 were reported in the placebo group.
Serious side effects associated with vaccination were also rare: less than 0.2% in people who received the vaccine. According to the study, most of the side effects reported were mild side effects, such as pain at the injection site, flu-like symptoms and low energy levels.
However, the analysis includes only symptomatic cases of Covid-19 and the authors note that more research is needed to understand the vaccine’s efficacy against asymptomatic Covid-19, transmission and duration of protection.
The majority of the study participants were also white, so further research is needed to confirm results among other ethical groups. The trial is also underway and aims for a total of 40,000 participants.
Dr. Inna V Dolzhikova, co-lead author of the study, said the analysis suggested the vaccine had “high efficacy, immunogenicity and a good tolerability profile in participants 18 years of age or older.”
Dolzhikova works at the Russian Gamaleya National Research Center for Epidemiology and Microbiology, which developed the vaccine.
The people in the trial were given PCR Covid-19 tests when they received the second injection. They took another test when they reported symptoms of a respiratory infection.
The Sputnik V vaccine is a two-dose adenoviral vector vaccine using two different adenoviruses for each dose, 21 days apart. This type of vaccine modifies an adenovirus so that it can release a piece of genetic material from the virus that causes Covid-19 in the body and cause the cells to express the virus’s peak induction and elicit an immune response. It is an approach similar to the vaccines developed by AstraZeneca and Johnson & Johnson.
The authors say that using a different adenovirus vector for the booster vaccination can help create a more potent immune response.
An advantage of adenoviral vaccines is that they don’t need to be stored and transported at extremely low temperatures, scientists say. Sputnik V only needs to be refrigerated and costs $ 10 per dose, according to Russian Direct Investment Fund, which funded vaccine production and is responsible for its worldwide sales.
“This is a useful addition to the published data on the effectiveness of the Covid-19 vaccine,” said Dr. Julian Tang, clinical virologist at the University of Leicester.
But he stressed that “the median follow-up was 48 days from the first dose, so the study cannot assess the full duration of protection.”
Production of the vaccine has been funded by the Russian Direct Investment Fund (RDIF), which is also responsible for its worldwide sales.
The vaccine has already been approved in Russia, Belarus, Serbia, Argentina, Bolivia, Algeria, Palestine, Venezuela, Paraguay, Turkmenistan, Hungary, United Arab Emirates, Iran, Guinea, Tunisia and Armenia. Sputnik V has been administered to more than 2 million people worldwide to date.
Russia faced criticism from scientific circles last year when it approved the Sputnik V for public use in August – before the pivotal Phase 3 studies were completed.
“Despite previous doubts about how this Russian Sputnik V vaccine was being rolled out more widely – pending sufficient Phase 3 research data – this approach is now to some extent justified,” said Tang.
CNN’s Meera Senthilingam, Jamie Gumbrecht, Jessica Firger and Zahra Ullah contributed to this report.