The fact that many Americans are saying they will not coronavirus vaccine is one of the reasons why the U.S. may never achieve herd immunity, says the country’s leading immunologist and disease expert Dr. Anthony Fauci.

Fauci believes that he would rather “settle” for a coronavirus vaccine that is 70 to 75% effective. That would not be full-proof protection and combining it with the fact that many people will refuse to get vaccinated against coronavirus, the U.S. may never achieve the immunity to stop the outbreak completely.

"The best we've ever done is measles, which is 97 to 98 percent effective. That would be wonderful if we get there. I don't think we will. I would settle for 70, 75% effective vaccine, " said Fauci, who is currently the director of the National Institute of Allergy and Infectious Diseases (NIAID).

When asked whether a coronavirus vaccine with 70 to 75 percent efficiency will help achieve herd immunity in the U.S., Fauci said it is not likely.

Herd immunity is achieved when a majority of the population is immune to an infectious disease. This is achieved either through vaccination or with a history of prior illness with the same disease. Achieving herd immunity makes it unlikely for the disease to spread from one person to the other.

At least three large-scale clinical trials of experimental coronavirus vaccines are expected to start in the U.S. next month.

Fauci expects the efficiency of the coronavirus vaccine to be less. On top of that, several people say that they will not get vaccinated.

A poll conducted in May 2020 revealed that nearly one-third of the Americans will not try to get vaccinates against COVID-19. They are not likely to change the decision even if the vaccine is widely available and affordable.

Fauci believes that it will be extremely hard to educate people about the coronavirus vaccine and why they must get it because he thinks that the “anti-vaccine movement” is extremely powerful at the moment.

"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 said.

Coronavirus COVID-19, Dr. Anthony Fauci, President Donald Trump Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, speaks as U.S. President Donald Trump looks on during a briefing on the coronavirus pandemic, in the press briefing room of the White House on March 24, 2020 in Washington, DC. Cases of COVID-19 continue to rise in the United States, with New York's case count doubling every three days according to Governor Andrew Cuomo. Drew Angerer/Getty Images