Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, said that to achieve herd immunity against COVID-19, 90 percent of the population would need to be vaccinated. In an interview published Thursday, Fauci acknowledged that he had gradually increased his estimates from earlier in the year when he said that around 60 or 70 percent of the population would need to be vaccinated to achieve herd immunity. Herd immunity is achieved when enough people in a population have immunity to an infection, whereby the chances of the disease being transmitted between people and reaching those who haven’t yet been infected is lowered, effectively preventing the disease from spreading. “We need to have some humility here,” Fauci told the New York Times. “We really don’t know what the real number is. I think the real range is somewhere between 70 to 90 percent. But, I’m not going …