Anthony Fauchi, a senior infectious disease specialist in the United States, said he had doubts about the safety of the Russian-made coronavirus vaccine.
He said this in an interview with National Geographic magazine.
According to Fauchi, the United States may introduce several coronavirus vaccines this week, but is not yet fully convinced of their effectiveness and safety. The use of a drug that has not yet passed all the necessary tests can not only give the desired effect, but also harm more people.
Earlier, US presidential aide Kellian Conway also criticized the Russian vaccine.
He said Russia's vehicle lagged behind that of the United States and had been poorly tested.