In recent days, a Vermont college suspended social gatherings after a spike in cases tied to Halloween parties. Boston officials shut down an elementary school to control an outbreak. Hospitals in New Mexico and Colorado are overwhelmed.

In Michigan, the three-county metro Detroit area is again becoming a hot spot for transmissions, with one hospital system reporting nearly 400 COVID-19 patients. Mask-wearing in Michigan has declined to about 25% of people, according to a combination of surveys tracked by an influential modeling group at the University of Washington.

“Concern over COVID in general is pretty much gone, which is unfortunate,” said Dr. Jennifer Morse, medical director at health departments in 20 central and northern Michigan counties. “I feel strange going into a store masked. I’m a minority. It’s very different. It’s just a really unusual atmosphere right now.”

New Mexico is running out of intensive care beds despite the state’s above-average vaccination rate. Waning immunity may be playing a role. People who were vaccinated early and have not yet received booster shots may be driving up infection numbers, even if they still have some protection from the most dire consequences of the virus.