"The answer is to be found in the human studies that will show how we respond to the vaccine", she said.
It is still not clear which vaccine will be effective. Each of the companies' vaccines are at various stages of development but have been deemed the most promising by the United States government.
"I'm cautiously optimistic that with the multiple candidates we have with different platforms, that we are going to have a vaccine that will make it deployable", Fauci said.
"Maybe we've got some work to do to try to explain exactly once we have the data, why these vaccines are in fact proven to be safe and effective", he said.
Hyundai's Santa Fe is even newer than it looks
There's also a new 10.25-inch infotainment system with pre-loaded maps and satellite-based voice-guided navigation. The centre console sits high, giving the driver and front passenger the feeling of sitting in an armchair.
The companies on the list are the farthest along in developing a vaccine and have significant manufacturing capacity.
The coronavirus vaccine may not grant full immunity after just one dose, according to a new report.
Fauci added that he is more concerned about the durability of response than whether the vaccine will achieve a protective response.
Fauci, director of the National Institute of Allergy and Infectious Diseases, said in an interview with the Journal of the American Medical Association that production of the vaccine would be done as it remains in its testing phase. "That is one of the reasons for doing the experiments and research trials to find out", he said.
Whatever the number of shots, Collins gave his personal promise that it wouldn't be rushed through.
Deliberately infecting humans with a pathogen of interest is normally "abhorrent", Caplan and Plotkin acknowledged, "but asking volunteers to take risks without pressure or coercion is not exploitation but benefitting from altruism", and extraordinary times, they said, sometimes require unconventional approaches.