"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.
On 11 August, Russia announced the world's first vaccine for COVID-19, named "Sputnik V", in a bid to curb the pandemic that has now killed over 737,000 globally.
Alongside Fauci, medical experts have also expressed concern about the safety of the vaccine, including a prominent pharmaceutical organisation in Russian Federation, the Association of Clinical Trials.
He said one of his two daughters has received a shot of the vaccine and is feeling well.
Philippine scientists were set on Wednesday to meet representatives of the Russian state research facility that developed a coronavirus vaccine, to discuss participation in clinical trials and access to its research data.
In July, Duterte made a plea to his Chinese counterpart to make the Philippines a priority if it develops a vaccine, amid concern in developing countries about availability. Mass roll-out in Russian Federation is expected to start in October.
Although he said the vaccine had passed all the required controls, noting that one of his daughters had already tested it, it is not on the World Health Organization's list of vaccines that have reached phase three clinical trials, which involve more widespread testing in humans.
Russian Federation will offer the vaccine to other countries when it has sufficient amounts, the minister said, adding that foreign nations' doubts about the effectiveness of the vaccine are unfounded.
Since the 1980s, the Gamaleya Centre has been developing a technological platform using adenoviruses found in human adenoids and normally transmitting the common cold, as vehicles, or "vectors", which could carry a genetic material from another virus into a cell. He added that the Indian government will also need to see how long the antibodies produced by the vaccine last. "The vaccine will not come tomorrow", he said.
Putin added that the vaccine, developed by Moscow's Gamaleya Institute, has proven efficient during tests and promises to offer "sustainable immunity" against the coronavirus.
On Tuesday, Russian Deputy Prime Minister Tatyana Golikova said that health workers will be the first to be vaccinated. Duterte volunteered to "be the first they can experiment on".
"I would be afraid of Russia's vaccine", Dr Bucaresky said in a telephone interview. But the decision has sent shock waves among virologists who could not lay their hands on any data related to the vaccine trials.
"But that's not the way it works", the infectious disease expert said.
Europe's Health chief, Stella Kyriakides has said that a possible vaccine for COVID-19 could be ready by the end of the year or by early 2021.