Retiring National Institutes of Health Director Francis Collins told Fox News on Friday that he was never asked to fire his nationally-recognized subordinate Anthony Fauci, despite the NIAID director's frequent clashes with Trump administration officials over federal coronavirus mitigation policy.

He also criticized former Trump coronavirus task force member Dr. Scott Atlas for touting herd immunity as a potential strategy for dealing with the pandemic.

Collins, 71, will leave the agency on Sunday after more than a decade in its top position. He told "Your World" that the new omicron variant of coronavirus will lead to a "tough couple of months" for the United States, based on its higher transmissibility than what he called the "original Wuhan virus" strain.

In a press release on Friday, Chairman James Clyburn, D-S.C., and the House Select Subcommittee on the Coronavirus Crisis wrote that Collins expressed "deep concerns about the herd immunity strategy being advocated by these ‘fringe epidemiologists’ and in an October 2020 email, called for "a quick and devastating published take down" of the herd immunity strategy known as "The Great Barrington Declaration."

Top infectious disease expert Dr. Anthony Fauci testifies before the Senate Health, Education, Labor, and Pensions Committee, July 20, 2021 on Capitol Hill in Washington, DC.  (Photo by J. Scott Applewhite-Pool/Getty Images) Dr. Francis Collins, Director of the National Institutes of Health, is seen (Photo by Greg Nash- Pool/Getty Images)

Top infectious disease expert Dr. Anthony Fauci testifies before the Senate Health, Education, Labor, and Pensions Committee, July 20, 2021 on Capitol Hill in Washington, DC.  (Photo by J. Scott Applewhite-Pool/Getty Images) Dr. Francis Collins, Director of the National Institutes of Health, is seen (Photo by Greg Nash- Pool/Getty Images) (J. Scott Applewhite-Pool/Getty Images; Greg Nash- Pool/Getty Images)

Host Neil Cavuto referenced the committee's findings and asked about the "take down" quotation.

"Well, OK, if it’s that specific. There were people [like] Scott Atlas that said don’t worry about this business of putting on masks or asking people to isolate themselves or stay distanced. Let it rip. Let this virus run through the country until everybody has had it, and we’ll have herd immunity’," Collins said.

"The consequence of that would have been hundreds of thousands of additional deaths," the Staunton, Va., native added. "That didn’t make sense to me."

In his own book about his time on the White House team, Atlas reciprocally ripped his fellow advisers, like Fauci and Dr. Deborah Birx, for often dismissing or disparaging his advice.

On "Your World", Collins further criticized herd immunity writ large, saying that with the virus' "capab[ility] to shape-shift, it gets in the way of herd immunity."

President Trump listens to White House coronavirus adviser Dr. Scott Atlas speak during a press conference in the Brady Briefing Room of the White House on September 23, 2020, in Washington, DC. (Photo by MANDEL NGAN / AFP)

President Trump listens to White House coronavirus adviser Dr. Scott Atlas speak during a press conference in the Brady Briefing Room of the White House on September 23, 2020, in Washington, DC. (Photo by MANDEL NGAN / AFP) (MANDEL NGAN/AFP via Getty Images)

"We might have herd immunity to the original Wuhan virus but not to omicron," he said. "It’s like we have a new character here, a screwed-up sibling of what we started with, and our immune system has potential to fight it off, but it’s challenging. So the herd immunity concept assumes that you deal with the same virus all the way along. This has not turned out to behave that way."

He also denied any allegations he was either pressured or instructed to fire Fauci after the immunologist's advice began clashing with Trump.

"No, I was never asked to do that. There were a lot of rumors flying around that that was about to happen," he said.

"I think I did several instances say I would not be willing to do that. Here’s probably the most respected knowledgeable infectious disease expert in the world who is basically getting in hot water because he’s speaking the truth to people that don’t want to hear it? Is that a reason for me to relieve him of his job? No. I would not have been willing to do that. They would have had to fire me first."

Collins said Fauci has "discharged his duties as a public servant in remarkable ways," and condemned threats and demonization the Brooklyn native is receiving from critics.

FILE - In this Dec. 12, 2020, file photo, President Donald Trump walks on the South Lawn of the White House in Washington before boarding Marine One. (AP Photo/Patrick Semansky, File)

FILE - In this Dec. 12, 2020, file photo, President Donald Trump walks on the South Lawn of the White House in Washington before boarding Marine One. (AP Photo/Patrick Semansky, File)

Collins later insinuated that he also clashed with Trump on occasion, but never thought he was in danger of being fired.

"I was in hot water a few times. I don’t think it ever came to the sort of sense of oh boy, I’m about to get that call. I got yelled at but I never got told you’re out of here," he said.

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"For me as a physician, as a scientist, also a person of faith, my anchor is truth. If I’m sticking to the truth and am not willing to compromise for some other expedient reasons, I think I’m doing the right thing. You know, if I lose my job on account of standing up for the truth, OK, I should lose the job."