Dr. Anthony Fauci, one of the the United States' leading experts on infectious diseases, warned Sunday, June 28 that it's "unlikely" the U.S. will achieve herd immunity to the coronavirus if a portion of the population refuses to get a coronavirus vaccine, CBS News reports.

In an interview that aired Sunday as part of the Aspen Ideas Festival, Fauci said he would "settle" for a coronavirus vaccine that is between 70% and 75% effective, "because that would bring you to that level that would be herd immunity level."

But when asked by CNN senior medical correspondent Elizabeth Cohen whether the U.S. can get to herd immunity if 25% of the population refuses to get a coronavirus vaccine with that rate of effectiveness, Fauci said, "No, unlikely."

Fauci, a member of the White House coronavirus task force, said the federal government has "a lot of work to do" in encouraging Americans to get inoculated once there is a coronavirus vaccine available to the public.

"There is a general anti-science, anti-authority, anti-vaccine feeling among some people in this country, an alarmingly large percentage of people relatively speaking," he said.