It comes as Mr Trump has repeatedly said a vaccine is possible before the November 3 election and accused a “deep state” within the nation’s top health regulator of trying to slow pivotal clinical trials to hamper his chances at a second term.
The US Food and Drug Administration refuted that claim, saying its decisions will be guided by data alone. Drugmakers, seeking to bolster public confidence amid political squabbles on Tuesday pledged to uphold scientific safety and efficacy standards in their quest for a vaccine.
However, comments from companies suggest they could have an answer on whether their vaccines work within that time frame.
Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told Reuters: “It would really be an amazing vaccine to show that.”
He said: “I just think humility is a good thing right now.
“The FDA set out some pretty strict criteria for success. So that’s going to take a pretty good vaccine to do that.”
Dr Henry Miller, a senior fellow at the Pacific Research Institute think tank and former director of the FDA’s office of biotechnology, said an emergency use authorization based on a small number of infections would not deliver an adequate answer on the safety of a vaccine intended for use by millions of healthy people.
Some side effects could take four to six months to occur, he said.