Russia has become the first country in the world to approve a coronavirus vaccine, Vladimir Putin has announced, amid concerns the process was rushed for political purposes.
The Russian president said that one of his daughters has already been inoculated and is "feeling well".
The announcement came after less than two months of human testing, sparking concerns that the country is putting national prestige before sound science and safety.
Scientists say the rush to start using the vaccine before Phase 3 trials - which usually last for months and involve thousands of people - could backfire.
But Mr Putin said the vaccine has undergone the necessary tests and has proven efficient, and offers a lasting immunity from COVID-19, paving the way for the mass inoculation of the Russian population.
Speaking at a government meeting, the Russian leader said: "I would like to repeat that it has passed all the necessary tests. The most important thing is to ensure full safety of using the vaccine and its efficiency."
He added that one of his two daughters "has taken part in the experiment" and has received two shots of the vaccine.
He explained that his daughter had a temperature of 38C on the day of the first vaccine, but it dropped to just over 37C the next day.
She had a slight increase in temperature following the second dose of the vaccine, but is now "feeling well and has a high number of antibodies".
Mr Putin did not specify which of his two daughters, Maria or Katerina, had received the vaccine.
The development has been hailed as a historic "Sputnik moment" by Kirill Dmitriev, head of Russia's sovereign wealth fund, who compared it to the Soviet Union's 1957 launch of Sputnik 1, the world's first satellite.
He added that the vaccine will be marketed under the name "Sputnik V" on foreign markets.
Speaking to Sky News, Mr Dmitriev said the vaccine is "great for the health and the economy of the world" and was "studied on thousands of people" before it was approved.
"No shortcuts were taken, basically Russia used the proven vaccine platform that was developed over six years by using two simple fluid viruses to deliver the spike of coronavirus," he said.
"It's a safe, very efficient approach. We believe the more vaccines are out there, the better it is for common people."
Russia has already received foreign requests for one billion doses, he said, and international agreements have been secured to produce 500 million doses annually.
The vaccine, developed by the Gamaleya Institute, is also expected to be produced in Brazil and clinical trials are expected to start soon in the United Arab Emirates and the Philippines.
Medical workers, teachers and other risk groups will be the first to be inoculated, Russian officials said.
Mr Putin emphasised that the vaccination will be voluntary.
Large-scale production of the vaccine is expected to start in September, and mass vaccination may begin as early as October.
Phase 3 trials are normally considered an essential step before a vaccine to receive regulatory approval.
Both domestic and international experts have expressed doubt at Moscow's claim.
The Association of Clinical Trials Organisations (ACTO), a Moscow-based trade body representing the world's top drugmakers in Russia, this week urged the country's health ministry to postpone approval until a final trial had been successfully completed.
In Germany, Peter Kremsner, from the University Hospital in Tuebingen, said: "Normally you need a large number of people to be tested before you approve a vaccine." He is currently testing CureVac's COVID-19 vaccine in clinical trials.
The UK's Foreign Secretary Dominic Raab said recently that he is "absolutely confident" Russian spies are trying to sabotage or steal UK scientists' coronavirus vaccine research, calling the action "outrageous and reprehensible".
He told Sky News it was important to call Mr Putin's government out for what he called "egregious" behaviour at a time when "the world is coming together" to battle the COVID-19 pandemic.
More than 100 possible vaccines are being developed, with at least four in Phase 3 human trials, according to WHO data.
The number of confirmed coronavirus cases around the world has reached 20 million, with experts believing the real figure is much higher.
Russia has nearly 800,000 confirmed COVID-19 cases and more than 15,000 deaths.