Outgoing National Institutes of Health Director Dr. Francis Collins took aim at the makers of the "The Great Barrington Declaration," refusing to step down from calling them "fringe epidemiologists" while arguing "hundreds of thousands" would have died of COVID-19 if the country followed their advice.

Collins told Fox News host Bret Baier Sunday that he was "not going to apologize" for comments Friday in front of the House Select Subcommittee on the Coronavirus Crisis in which he called advocates of herd immunity "fringe epidemiologists," arguing that "hundreds of thousands of people would have died if we had followed that strategy."

MEDIA FACT-CHECKERS, FACEBOOK CITED WUHAN LAB-LINKED SCIENTIST TO KNOCK DOWN LAB LEAK THEORY

NIH Director Dr. Francis Collins testifies before a hearing looking into the budget estimates for National Institute of Health (NIH) and the state of medical research on Capitol Hill in Washington, DC on May 26, 2021.

NIH Director Dr. Francis Collins (Sarah Silbiger / POOL / AFP) (Photo by SARAH SILBIGER/POOL/AFP via Getty Images)

"I did write that, and I will stand by that," Collins said. "Basically, these fringe epidemiologists who really did not have the credentials to be making such a grand sweeping statement, were saying just let the virus run through the population and eventually then everybody would have had it and everything will be okay."

But hundreds of thousand of Americans have died of COVID-19 on his watch, with the most recent Centers for Disease Control and Prevention numbers showing over 800,000 have lost their lives to the disease since the beginning of the pandemic. 

Yet Collins called for a "quick and devastating published takedown" of the three experts pushing for a herd immunity strategy, which The Great Barrington Declaration largely pushes for.

Left: Dr. Anthony Fauci. Right: Dr. Francis Collins (J. Scott Applewhite-Pool/Getty Images; Greg Nash- Pool/Getty Images)

"So I'm sorry I was opposed to that, I still am, and I'm not going to apologize for it," Collins said.

Collins, who made the Fox News appearance during his last day on the job as NIH director, also pushed back against rumors that he was stepping aside because of his agency's alleged involvement in gain-of-function research in China, arguing that the theory COVID-19 leaked from a Chinese lab was a "huge distraction."

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Peter Daszak and Thea Fischer, members of the World Health Organization (WHO) team tasked with investigating the origins of the coronavirus disease (COVID-19), sit in a car arriving at Wuhan Institute of Virology in Wuhan, Hubei province, China February 3, 2021. REUTERS/Thomas Peter (REUTERS/Thomas Peter)

"There is no evidence really to say. Most of the scientific community, myself included, think that is a possibility, but far more likely, this was a natural way in which a virus left a bat, maybe traveled through some other species and got to humans," Collins said.

Collins, a geneticist and physician tapped by former President Barack Obama, will step down after more than a decade on the job, having taken over the position in 2009.

The NIH did not immediately respond to Fox News when asked for further comment.