Russia approved a coronavirus vaccine before confirming it was safe and effective. Experts say the nation's risky bet paid off.

• Russia's coronavirus vaccine, called Sputnik V, is 91.6% effective at preventing symptomatic COVID-19, according to a peer-reviewed analysis published Tuesday.
• The country approved its vaccine in August, before conducting late-stage clinical trials.
• Experts worried the controversial approach might overlook potentially dangerous side effects — but the new results indicate that Russia's risky bet may have paid off.

Russia became the first country to approve a coronavirus vaccine in August and start distributing shots in early December. Now it has some reliable data that those vaccines may be about as effective as those authorized for emergency use in the US and UK.

Unlike the US or UK, Russia approved its vaccine - called Sputnik V - before conducting phase 3 trials. These late-stage trials typically evaluate a medical treatment in tens of thousands of people to determine how well it works, ensure that it's safe, and uncover any side effects.

When Russia approved Sputnik V for distribution, only 38 people had received the vaccine in clinical trials. All of them produced antibodies, and side effects were mostly mild - including elevated temperatures and headaches. That research had not undergone peer review, though.

As Sputnik V was distributed to frontline healthcare workers in December, medical experts warned that the data was insufficient to determine whether the vaccine was safe and effective. Some scientists suggested that the vaccine approval may have been rushed for political reasons.

But Russia's risk seems to be paying off. An interim analysis of phase 3 trials published in The Lancet on Tuesday suggests that Sputnik V is 91.6% effective at preventing symptomatic COVID-19.

"I think everything has been done perfectly and this moment is in some ways a vindication moment," Kirill Dmitriev, CEO of the Russian Direct Investment Fund (RDIF), told Insider in an exclusive interview on Tuesday. The RDIF is one of the world's largest sovereign wealth funds, and has overseen and financed the development of Sputnik V.

Dr. Julian Tang, a consultant virologist at the UK's University of Leicester, told Insider the nation's risky approach "has been justified to some extent now."

Russia plowed forward on vaccinations, despite blowback

Sputnik V is given in two doses. Each dose relies on a different adenovirus - relatively harmless viruses associated with the common cold - to deliver a gene that codes for the coronavirus' spike protein, which helps it attach to and invade cells. In theory, this should train the immune system to produce antibodies that ward off symptomatic disease.

The Gamaleya Institute in Moscow and the Russian Ministry of Defence developed the vaccine in tandem.

Russian President Vladimir Putin announced on August 11 that the country's health agency had approved the new vaccine following phase 1 and 2 clinical trials. Some virus experts feared that any severe side effects missed in those early trials could undermine public trust in other vaccines, too.

"This is a reckless and foolish decision. Mass vaccination with an improperly tested vaccine is unethical. Any problem with the Russian vaccination campaign would be disastrous both through its negative effects on health, but also because it would further set back the acceptance of vaccines in the population," Francois Balloux, a geneticist at University College London, said in a statement distributed by the UK Science Media Centre.

Despite these concerns, Russia's health ministry began producing batches of the vaccine in August. By December, the country was offering its first doses to essential workers like teachers and healthcare professionals.

"We registered it in August why? Because we know it's a safe human adenoviral platform tested for decades. It's very different from an mRNA vaccine that has not been tested long term at all," Dmitriev said. "So we do it and we give it only to high risk personnel who wants to take it. And therefore already in September, we were able to save people, protect lives, and to create this basically safety net of some of the high risk personnel."

Phase 3 trials were ongoing at the time, but it would be months before they produced reliable results.

'Good news' from phase 3

In November, Russia announced that preliminary data from phase 3 trials showed that its vaccine was 92% effective at preventing COVID-19. But the data was based on just 20 confirmed COVID-19 cases, split between the group of participants that had been vaccinated and the group that had received a placebo, according to a press release. It had not yet undergone peer review.

The peer-reviewed analysis published Tuesday, however, was based on a group of nearly 15,000 people who received the Sputnik V doses. Of that group, only 16 people had confirmed COVID-19 cases 21 days after their first dose, compared to 62 out of 4,902 people in the placebo group. None of the vaccinated people had moderate or severe symptoms.

The phase 3 trial relied on participants to self-report any symptoms in order to test and identify new cases post-vaccination. But researchers still don't know how effective Sputnik V is at preventing asymptomatic infection or transmission. The US is missing the same data for both the Pfizer and Moderna vaccines.

"The development of the Sputnik V vaccine has been criticized for unseemly haste, corner cutting, and an absence of transparency," British virologists Ian Jones and Polly Roy wrote in an editorial accompanying the new study on Tuesday. "But the outcome reported here is clear and the scientific principle of vaccination is demonstrated, which means another vaccine can now join the fight to reduce the incidence of COVID-19."

Ashish Jha, dean of the Brown University School of Public Health, called the results "good news."

"We need all the safe effective vaccines we can get," he wrote on Twitter.

Sixteen foreign countries or sovereign states have already approved Russia's shots: Belarus, Argentina, Bolivia, Serbia, Algeria, Palestine, Venezuela, Paraguay, Turkmenistan, Hungary, United Arab Emirates, Iran, Guinea, and Tunisia.

Dmitriev said he expects Sputnik V to be registered in 25 nations by the end of next week, but applying for regulatory approval in the US and UK isn't a priority.

Andrew Dunn, Dr. Catherine Schuster-Bruce, Sinéad Baker, and Susie Neilson contributed reporting.