CNN anchor John Berman noted that Tucker Carlson had questioned the efficacy of the vaccines after public health officials have encouraged those who have been vaccinated to carry on wearing masks and social distancing for the time being.
Mr Carlson said: "If the vaccine is safe, there is no reason for people who have received the vaccine to wear masks or avoid physical contact. So maybe it doesn't work and they're simply not telling you that."
"That's just a typical crazy conspiracy theory," Dr Fauci responded.
"The data are overwhelming in the three vaccines used in emergency use and emergency use authorization: The J&J, Pfizer, and Moderna, you had 30,000, 44,000, and 40,000 people in the clinical trial with an overwhelming signal of efficacy. So I don't have any idea what he's talking about," he said, referring to the Fox News host.
Mr Berman asked Dr Fauci how dangerous it is for a TV host with an audience of millions "to speculate about something like that".
"It's certainly not helpful to the public health of this nation or globally. I don't want to get into arguments about Tucker Carlson, but to me, it's counter to trying to protect the safety and health of the American public," Dr Fauci said.
Mr Berman asked Dr Fauci what his message was to those who are slightly hesitant about getting inoculated and have a "wait and see" approach.
"It's understandable why people do that, you don't want to be pejorative against them," Dr Fauci said. "That's a natural instinct of wanting to wait and see. But what you tell people is 'let's look at the data'. We have over 120, close to 130 million people [who] have already received at least one dose of this. That's a lot of people, how long do you want to wait and see?"
"Almost half the country has received at least one dose, so I think we've had enough 'wait and see' – let's do it,” he added.
Mr Berman pointed out that 3.4 million people on average get vaccinated every day. "A remarkable number, an astounding number, which should be celebrated," he said.
Cases have risen to "nearly 80,000 cases a day now" the CNN host noted. Striking an optimistic tone, he asked if we might be able to see fewer deaths and fewer hospitalisations even as cases rise because "the most vulnerable population has been vaccinated".
"Is it possible we might see a drop in deaths no matter what happens with cases?" he asked.
"Yeah ... I think that's exactly what's going to happen because if you look at the people who are most vulnerable to death, namely the elderly ... more than 76 per cent of people over 65 ... have been vaccinated,” Dr Fauci said.
He added that as more and more people are vaccinated every day, "you are going to see cases come down".
Join our new commenting forum
Join thought-provoking conversations, follow other Independent readers and see their replies