Top U.S. infectious disease expert Anthony Fauci warned that the U.S. is "unlikely" to achieve herd immunity to the novel coronavirus once a vaccine is available.

He said the vaccine would be only 70 percent to 75 percent effective because many Americans refuse to get it.

"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," Fauci told CNN in an interview.

As of Monday morning, the U.S. reported more than 2.5 million cases of COVID-19, with 125,808 deaths, according to the latest tally from Johns Hopkins University.

(Cover: Reuters file photo)