Younger, unvaccinated people appear to be driving the latest uptick in Covid-19 cases while vaccines are reducing the toll for older persons

Covid cases are rising again. Who's getting sick? Younger, unvaccinated people appear to be driving the latest uptick in Covid-19 cases. NBC News

People under 60 are accounting for the majority of new Covid-19 cases across the country — likely a testament to the success of the vaccines that have been administered to primarily older, more vulnerable Americans.

The number of cases is rising again following a steep decline and then plateauing for several weeks. During a White House Covid-19 briefing Monday, Centers for Disease Control and Prevention director Dr. Rochelle Walensky said the rise in cases — an average increase of 10 percent from the previous week — gave her a sense of "impending doom."

But doctors say that patients seeking care this time around are younger and, notably, not as sick.

In New York, where cases are rising, some Covid-19 patients still require hospitalization, but the numbers of such patients are nowhere near the "astronomical" levels from a year ago, said Dr. Frederick Davis, an associate chair of emergency medicine at Northwell Health's Long Island Jewish Hospital.

Now, Davis said, Covid-19 cases are mostly mild.

"The cases we are seeing are the younger groups that probably aren't eligible for vaccines just yet," Davis said.

More than 73 percent of people over age 65 has received at least one dose of the Covid-19 vaccine, and nearly half are fully vaccinated. Monday, the CDC reported that the Pfizer-BioNTech and Moderna vaccines are 90 percent effective against Covid-19 in the real world.

The increase in immunity among older adults is illustrated in the shift in age groups most likely to seek care for Covid-19.

Nationwide, "the number of 25-to-49-year-olds visiting U.S. emergency departments for diagnosed Covid-19 is now higher than the number of visits among patients 65 and older," the CDC said in a statement to NBC News. ...