“The best we’ve ever done is measles, which is 97 to 98 percent effective,” said Fauci, the director of the National Institute of Allergy and Infectious Diseases. “That would be wonderful if we get there. I don’t think we will. I would settle for [a] 70, 75% effective vaccine.”

A CNN poll last month found one-third of Americans said they would not try to get vaccinated against Covid, even if the vaccine is widely available and low cost.

In an interview Friday, CNN asked Fauci whether a vaccine with 70% to 75% efficacy taken by only two-thirds of the population would provide herd immunity to the coronavirus.

“No — unlikely,” he answered.