Is herd immunity possible?

It’s not likely for the country as a whole. Because the British variant now circulating in the U.S. is estimated to be 60 percent more infectious, most virologists now believe about 80 percent of Americans will need immunity through prior infections or vaccination to achieve classic herd immunity, where transmission stops. Marc Lipsitch, an epidemiologist at the Harvard T.H. Chan School of Public Health, cautions that “disease transmission is local” and may