Michael Osterholm, a renowned infectious-disease expert, said on NBC's "Meet the Press" Sunday that a "herd immunity" theory reportedly invoked by one of President Trump's favorite coronavirus advisers "is the most amazing combination of pixie dust and pseudoscience I've ever seen."

Context: Senior administration officials, who spoke anonymously with reporters last week in a call scheduled by the White House, said that allowing "those who are at minimal risk of death to live their lives normally to build up immunity to the virus through natural infection" is the "most compassionate approach that balances the risks and benefits of reaching herd immunity," per the New York Times and Washington Post.

• Achieving herd immunity — in which widespread outbreaks are prevented because enough people in a community are immune to a disease — without an effective vaccine would result in widespread fatalities.

Driving the news: Scott Atlas, a radiologist who has clashed with other members of the coronavirus task force over his controversial views, reportedly turned down a proposed increase in coronavirus testing by a New York University economist in September by referencing a theory that only 25% or 20% of people need the infection for the rest of the population to be protected, according to the New York Times.

What they're saying: "First of all, that 20% number is the most amazing combination of pixie dust and pseudoscience I've ever seen," Osterholm said in response to Atlas' alleged comments. "It is 50 to 70% at minimum."

• "And remember when we talk about getting to 50 to 70% protection, we're talking you can get there with disease — but if that happens, there will be lots of deaths, lot of serious illnesses — or we can try to get there with vaccination, and postponing the number of people who get sick until we have the vaccines available."
• "5o to 70% just slows down transmission, it doesn't stop it. So this virus is going to keep looking for wood to burn for as long as it can ... so, our goal is to get as many people protected with vaccines," he said.

The other side: Health and Human Services Secretary Alex Azar told NBC's Chuck Todd on Sunday that herd immunity is not the Trump administration's policy to deal with the pandemic, adding: "It's a desire through vaccination to get to herd immunity, but it may be an outcome of all of those steps, but the desire is reduce cases."

• White House press secretary Kayleigh McEnany told reporters last month that "herd immunity has never been a strategy" for the Trump administration's response to the coronavirus, after the president claimed that the coronavirus would disappear when people develop "a herd mentality."

The big picture: Osterholm warned that the U.S. is likely to "blow right through" its July peak in infections, with case numbers "much larger" than 75,000 per day as the country barrels toward a "very dark fall."

Go deeper: Twitter removes tweet from Scott Atlas claiming masks do not work