MISSION, Kan. — The number of COVID-19 deaths and cases in the U.S. have returned to levels reached last winter, potentially bolstering President Joe Biden’s argument for sweeping new vaccination requirements.

The U.S. is averaging more than 1,800 COVID-19 deaths and 170,000 new cases per day. That’s still well below the peak of about 3,400 deaths and 250,000 cases per day in January. But it’s frustrating health care leaders, nine months into the nation’s vaccination drive, who are watching hospitals fill up with unvaccinated patients.

The cases, driven by the delta variant and resistance among some Americans to get vaccinated, are concentrated mostly in the South.

While hot spots such as Florida and Louisiana are improving, infection rates are soaring in Kentucky, Georgia and Tennessee, fueled by children back in school, loose mask requirements and low vaccination rates.

“Now in Kentucky, one-third of new cases are under age 18,” says Dr. Ryan Stanton, an emergency room physician in Lexington. He says some children brought it home from summer camp and spread it to the rest of the family, and “between day care and schools and school activities, and friends getting together, there are just so many exposures.”