President Vladimir Putin said a coronavirus vaccine developed in Russia has been approved for use, despite not undergoing clinical tests and no data being made public.
Putin made the announcement at a government meeting on August 11, saying the vaccine had proven to be "efficient" during initial tests and could provide lasting immunity from the coronavirus.
More than 100 possible vaccines are being developed around the world, and at least four are in final Phase 3 of testing in human trials.
Phase 3 trials usually involve thousands of people and last for months, according to the World Health Organization (WHO).
Russia is the first country to register a coronavirus vaccine. But scientists within Russia and abroad have voiced skepticism, questioning the decision to register the vaccine before Phase 3 trials have been completed.
The WHO last week urged Russia to follow established guidelines and go "through all the stages" necessary to develop a safe vaccine.
But Putin insists that the Russian vaccine underwent the necessary tests, adding that one of his two daughters had received it and was feeling well.
"I hope that we will be able to begin mass production in the near future, which is important," Putin said, stressing that inoculation "should be done on a strictly voluntary basis."
Russia's government has said that health workers, teachers, and people in other high-risk categories will be the first to be offered the vaccine.
Russia has nearly 860,000 registered cases of COVID-19 -- the fourth-highest number in the world -- and more than 14,300 deaths, according to a global tally kept by Johns Hopkins University.
The World Health Organization's spokesman in Geneva, Tarik Jasarevic, said it was in "close contact" with Russian health authorities but that it was too soon for any approval.
"Prequalification of any vaccine includes the rigorous review and assessment of all the required safety and efficacy data," he said.
A spokesman for the German Health Ministry told the newspaper group RND that "there is no known data on the quality, efficacy, and safety of the Russian vaccine," adding that "patient safety is of the highest priority."
Meanwhile, the Pan American Health Organization expressed concerns that some institutions in the region were negotiating to manufacture and distribute any COVID-19 vaccine from Russia without standard safety and efficacy trials.
U.S. Health Secretary Alex Azar, asked about Russia's announcement, said safety was paramount and late-stage trials were key. He said the United States was on track for an effective vaccine by the end of the year, with six candidates under development.
"The point is not to be first with a vaccine. The point is to have a vaccine that is safe and effective," Azar told ABC.
"We hope it's true, but as is so often the case with Russia: trust but verify," the acting chairman of the White House Council of Economic Advisers, Tyler Goodspeed, said on the Fox Business Network, referencing a Russian proverb cited by former U.S. President Ronald Reagan in negotiations with the Kremlin.