Russia has dismissed mounting international concern over the safety of its locally developed Covid-19 vaccine as "absolutely groundless".
But experts were quick to raise concerns about the speed of Russia's work, and a growing list of countries have expressed scepticism.
Scientists in Germany, France, Spain and the US have all urged caution, BBC reported.
"It seems our foreign colleagues are sensing the specific competitive advantages of the Russian drug and are trying to express opinions that... are absolutely groundless," Russia's Health Minister Mikhail Murashko told the Interfax news agency on Wednesday.
He added that the vaccine would be available soon.
"The first packages of the medical vaccine... will be received within the next two weeks, primarily for doctors," Mr Murashko said.
The announcement on Tuesday was made by President Vladimir Putin, who said the vaccine had passed all the required checks and his daughter had already been given it.