But national averages mask the high rate of older Americans who remain deeply vulnerable. Older people still account for most Covid-19 deaths, and in many counties, especially in the South and Mountain West, seniors without full vaccination make up more than 10 percent of the total population.

“We have swaths of populations in counties who are healthy Americans, over 60, who are not vaccinated,” said Claire Hannan, executive director of the Association of Immunization Managers. “These people are at extreme risk, and they don’t realize it.”