Now, more than half of adults in the United States have been inoculated with at least one dose of a vaccine. But daily vaccination rates are slipping, and there is widespread consensus among scientists and public health experts that the herd immunity threshold is not attainable — at least not in the foreseeable future, and perhaps not ever.
Instead, they are coming to the conclusion that rather than making a long-promised exit, the virus will most likely become a manageable threat that will continue to circulate in the United States for years to come, still causing hospitalizations and deaths but in much smaller numbers.
How much smaller is uncertain and depends in part on how much of the nation, and the world, becomes vaccinated and how the coronavirus evolves. It is already clear, however, that the virus is changing too quickly, new variants are spreading too easily and vaccination is proceeding too slowly for herd immunity to be within reach anytime soon.
Continued immunizations, especially for people at highest risk because of age, exposure or health status, will be crucial to limiting the severity of outbreaks.
“What we want to do at the very least is get to a point where we have just really sporadic little flare-ups,” said [evolutionary biologist] Carl Bergstrom.