The preliminary findings were published in The Lancet on Tuesday and are based on data collected from 19,866 participants, of whom about 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 participants received the first dose of vaccine. Sixty-two cases were found in the placebo group, which equates to an efficiency of 91.6%.
The trial included 2,144 people older than 60 years and a sub-analysis done on this group revealed that the vaccine is well tolerated and has a similar 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 vaccine-related side effects were also rare – less than 0.2% in people who received the vaccine. According to the study, most side effects were mild, such as injection site pain, flu-like symptoms and low energy levels.
However, the analysis contains only symptomatic cases of Covid-19, and the authors note that more research is needed to understand the efficacy of the vaccine against asymptomatic Covid-19, transmission and how long protection may last.
The majority of participants in the trial were also white, and therefore further research is needed to confirm the results in other ethical groups. The trial is also continuing and aims to include a total of 40,000 participants.
Dr. Inna V Dolzhikova, co-lead author of the study, said the analysis suggested that the vaccine has a high efficacy, immunogenicity and a good tolerance profile in participants 18 years or older.
Dolzhikova works at the Russian Gamaleya National Research Center for Epidemiology and Microbiology, which developed the vaccine.
The people in the trial got PCR Covid-19 tests when they got the second shot. They took a further test if they had symptoms of respiratory infection.
The Sputnik V vaccine is a two-dose adenoviral vector vaccine that uses two different adenoviruses for each dose, with doses administered 21 days apart. With this type of vaccine, an adenovirus is altered so that it can deliver a piece of genetic material from the virus that causes Covid-19 in the body and get cells to express the peak induce that occurs on the virus and an immune response to cause. This is an approach similar to the vaccines developed by AstraZeneca and Johnson & Johnson.
The authors say that using a different adenovirus vector for booster vaccination may help create a more potent immune response.
One benefit of adenoviral vaccines is that they do not need to be stored and transported in extremely cold temperatures, scientists say. Sputnik V only needs to be in the fridge and costs $ 10 per dose, according to Russian Direct Investment Fund, which funds vaccine production and is responsible for selling it worldwide.
“This is a useful addition to the published data on the efficacy of the Covid-19 vaccine,” said Dr. Julian Tang, clinical virologist at the University of Leicester, said.
But he stressed that “median follow-up was 48 days from the first dose, so the study could not assess the full duration of protection.”
The production of the vaccine is financed by the Russian Direct Investment Fund (RDIF), which is also responsible for selling it worldwide.
The vaccine has already been approved in Russia, Belarus, Serbia, Argentina, Bolivia, Algeria, Palestine, Venezuela, Paraguay, Turkmenistan, Hungary, UAE, Iran, Guinea, Tunisia and Armenia. Sputnik V has so far been administered to more than 2 million people worldwide.
Russia drew criticism from scientific circles last year when it approved Sputnik V for public use in August – before the important Phase 3 trials were completed.
“Despite earlier concerns about the way in which this Russian Sputnik V vaccine has been expanded – before sufficient Phase 3 trial data – this approach is justified to some extent,” Tang said.
CNN’s Meera Senthilingam, Jamie Gumbrecht, Jessica Firger and Zahra Ullah contributed to this report.