Pecker is a key witness in the case against the former US president, who is accused of falsifying business records to cover up hush-money payment
Chuchalin's resignation suggests that the vaccine, dubbed "Sputnik V", faced criticism from within the country also.
The MailOnline report also said that no specific reason was given for his resignation.
However, shortly before he quit, Chuchalin in an interview with journal Nauka i Zhizn (Science and Life) underlined the importance of ensuring safety before approving any drug or vaccine.
"In the case of a drug or vaccine, we, as ethical reviewers, would like to understand, first of all, how safe it is for humans," Chuchalin was quoted as saying in the interview.
Pecker is a key witness in the case against the former US president, who is accused of falsifying business records to cover up hush-money payment
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