You must have missed it - its in the article itself. >But as vaccines were developed and distribution ramped up through the winter and into the spring, estimat

You must have missed it - its in the article itself. >But as vaccines were developed and distribution ramped up through the winter and into the spring, estimates of the threshold began to rise. That is because the initial calculations were based on the contagiousness of the original version of the virus. The predominant variant now circulating in the United States, called B.1.1.7 and first identified in Britain, is about 60 percent more transmissible. >As a result, experts now calculate the herd immunity threshold to be at least 80 percent. If even more contagious variants develop, or if scientists find that immunized people can still transmit the virus, the calculation will have to be revised upward again. >Though resistance to the vaccines is a main reason the United States is unlikely to reach herd immunity, it is not the only one >“Disease transmission is local,” Dr. Lipsitch noted. >“If the coverage is 95 percent in the United States as a whole, but 70 percent in some small town, the virus doesn’t care,” he explained. “It will make its way around the small town.” >At the same time, the connectivity between countries, particularly as travel restrictions ease, emphasizes the urgency of protecting not just Americans but everyone in the world, said Natalie E. Dean, a biostatistician at the University of Florida in Gainesville. Any variants that arise in the world will eventually reach the United States, she noted.