Britain and Israel, which both have higher vaccination rates than the United States, are still struggling with outbreaks.
“That should be a wake-up call,” said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. “Do not go back into the pre-Fourth-of-July mind-set again, where everybody thought it was done and over with.”
Most experts said they would not be surprised to see at least a small increase in cases later this fall or this winter as people begin spending more time indoors and traveling for the holidays.
But because the vaccines remain highly effective at preventing hospitalization and death, any coming winter spikes may be less catastrophic than last year’s.
“It’s not likely that it will be as deadly as the surge we had last winter, unless we get really unlucky with respect to a new variant,” Dr. Salomon said.
The emergence of a new variant remains a wild card, as does the possibility that the protection afforded by vaccination could start to wane more substantially.
Our own behavior is another source of uncertainty.
“Predicting an outbreak is not like predicting the weather, because you’re dealing with human behavior,” said Nicholas Reich, a biostatistician at the University of Massachusetts, Amherst. “And that’s a fundamentally really hard thing to predict: new policies that would come into force, people’s reactions to them, new trends on social media, you know — the list goes on and on.”