Russia was the first nation to approve the rollout of a COVID vaccine in August of 2020, and as of Tuesday (Feb. 2), the country's Sputnik V vaccine has proven to be 91.6% effective against symptomatic COVID-19 and 100% effective against severe and moderate disease, according to an interim analysis of the vaccine's Phase 3 trial results.

CNN reports that the preliminary findings were published in The Lancet on Tuesday and are based on data gathered from 19,866 participants, of which around three-quarters (14,964) received two doses of the vaccine and a quarter (4,902) were given a placebo.

Sixteen cases of symptomatic COVID-19 were found in the vaccine group 21 days after participants received the first vaccine dose. Sixty-two cases were confirmed in the placebo group, equating to 91.6 percent effectiveness.

The trial consisted of 2,144 people over the age of 60, and a sub-analysis conducted on this group revealed the vaccine was well tolerated and had a similar efficacy of 91.8%.

The team also studied the effectiveness of the vaccine against severe and moderate COVID-19 disease and 21 days after the first dose no severe or moderate cases were reported in the vaccinated group, while 20 were reported in the placebo group.

Severe adverse events associated with vaccination were also rare, occurring in less than 0.2% in people who received the vaccine. The majority of side-effects reported were mild side and included pain at the injection site, flu-like symptoms, and low energy levels.

According to CNN, the analysis includes only symptomatic cases of COVID-19, however, and the authors note more research is needed to understand the vaccine's efficacy against asymptomatic COVID-19, transmission and how long protection may last.

Dr. Inna V Dolzhikova, co-lead author of the study and employed by the organization that developed the vaccine, Russia's Gamaleya National Research Centre for Epidemiology and Microbiology, praised the vaccine.

Dolzhikova said the analysis suggested the vaccine had "high efficacy, immunogenicity, and a good tolerability profile in participants aged 18 years or older." 

Trial participants were given PCR COVID-19 tests when they received the second shot. They took an additional test if they reported symptoms of respiratory infection.

The Sputnik V vaccine is a two-dose adenoviral vector vaccine using 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 into the body and get cells to express the spike induce found on the virus and induce an immune response. According to CNN, this 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 may help create a more powerful 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 refrigerated and costs $10 per dose, according to Russian Direct Investment Fund, which funded vaccine production and is responsible for selling it globally.

"This is a useful addition to the published data on COVID-19 vaccine effectiveness," Dr. Julian Tang, clinical virologist at the University of Leicester.

But he added that "median follow up was 48 days from the first dose, so the study cannot assess the full duration of protection."

The vaccine is currently approved in Russia, Belarus, Serbia, Argentina, Bolivia, Algeria, Venezuela, Paraguay, Turkmenistan, Hungary, UAE, Iran, Guinea, Tunisia, Armenia and the Palestinian territories. So far, Sputnik V has been administered to more than 2 million people worldwide.