Unlike last winter’s concerted federal push to vaccinate residents and staff in nursing homes, the booster rollout has been sluggish and piecemeal, health experts said. Public information is sparse: About 42 percent of Americans over 65 have received a booster shot, according to federal reports, but there is no data available yet on U.S. sites to track nursing home booster programs.

The staggering Covid death toll at nursing homes in 2020, steep declines in cases after the successful vaccine campaign and then the steady rise again in late summer and this fall should have made boosters for older Americans a top priority, some experts say.

“What’s been surprising is the lack of data and attention on nursing homes this time around,” said Dr. Ashish Jha, a physician and dean of the Brown University School of Public Health. The government should have authorized additional doses as early as July, he noted, especially since nursing home residents were among the first to receive the vaccines 10 or more months ago.

“The data was clear at that point,” Dr. Jha said. “We were seeing waning immunity, particularly in the elderly.”