Russian scientists say the country’s Sputnik V vaccine appears safe and effective against the coronavirus disease 2019 (Covid-19), according to early results of an advanced study published in a British medical journal.

Researchers said, based on their trial that involved about 20,000 people in Russia last fall, the vaccine is about 91-percent effective and appears to prevent people from becoming severely ill with Covid-19. The study was published online Tuesday in the journal The Lancet.

The news is a boost for the shot that is increasingly being purchased by nations around the world who are desperate to stop the devastation caused by the pandemic.

Scientists not linked to the research acknowledged that the speed at which the Russia vaccine was made and rolled out was criticized for “unseemly haste, corner cutting and an absence of transparency.”

“But the outcome reported here is clear,” British scientists Ian Jones and Polly Roy wrote in an accompanying commentary. “Another vaccine can now join the fight to reduce the incidence of Covid-19.”

“This is a great day in the fight against the Covid-19 pandemic,” said Kirill Dmitriev, CEO of the Russian Direct Investment Fund that bankrolled the development of the shot.

The Sputnik V vaccine was approved by the Russian government with much fanfare on Aug. 11. President Vladimir Putin personally broke the news on national television and said one of his daughters had already been vaccinated with it. At the time, the vaccine had only been tested in several dozen people.

Some early results on it were published in September, but participants had only been followed for 42 days and there was no comparison group.

BASED ON LATEST STUDIES

The latest study is based on research involving about 20,000 people over 18 at 25 hospitals in Moscow between September and November, of whom three-quarters got two doses of the Russian vaccine 21 days apart and the remainder got placebo shots.

The most commonly reported side effects were flu-like symptoms, pain at the injection site and fatigue. Serious side effects were rare in both groups and four deaths were reported, although none were considered to be the result of the vaccine.

The study included more than 2,100 people over 60 and the vaccine appeared to be about 92-percent effective in them. The research is ongoing but in December, Russia’s Health Ministry said it was cutting the size of the study from the planned 40,000 subjects to about 31,000 volunteers who have already enrolled. Developers of the vaccine cited ethical concerns about using placebo shots.

The Russian vaccine uses a modified version of the common cold-causing adenovirus to carry genes for the spike protein in the coronavirus as a way to prime the body to react if Covid-19 comes along. That’s a similar technology to the vaccine developed by AstraZeneca and Oxford University. But unlike AstraZeneca’s two-dose vaccine, the Russians used a slightly different adenovirus for the second booster shot.