Rates of children hospitalized with COVID have reached an all-time high in the US

• Average daily hospitalizations of children with COVID have reached an all-time high of 239.
• The rate is higher for adults: in the under-vaccinated Southeast, the daily rate of overall hospitalizations jumped last week to 17,600.
• Experts urge masking in schools, but the states with the most kids hospitalized have already banned mask mandates.

More kids than ever are landing in the hospital with severe illness as the Delta variant drives a surge in COVID cases in the US.

Hospital admissions of children with COVID-19 have reached a peak that has officially exceeded that of the winter surge, according to data from the Centers for Disease Control and Prevention.

An average of 239 children per day were admitted to the hospital with COVID between August 3 and 9, which is the most recent data set available on the CDC site. At the pandemic's peak in early January 2021, the average number of pediatric admissions per day reached 217, The New York Times reported. (The rate is higher for adults: in the under-vaccinated Southeast, the daily rate of overall hospitalizations jumped last week to 17,600.)

Pediatric cases and hospital admissions have been on the rise since early July, following a lull in the early summer. The definition of "child" cases varies from state to state, but loosely includes individuals of age 17 or younger.

Nearly 94,000 new child COVID-19 cases were reported the week ending August 5, according to a weekly report from the American Academy of Pediatrics. That means kids make up about 15% of weekly total cases in the US, the report said.

Experts say it's not yet clear whether the Delta variant causes especially severe disease in children, but one thing is certain: the fact that the Delta variant is highly infectious is driving a surge in pediatric cases and hospitalizations.

Hospitalizations among children are increasing 'exponentially'

Severe illness due to COVID-19 is still relatively uncommon among children, with kids making up between 1.5% and 3.5% of total hospitalizations nationwide, according to the AAP report.

Still, a highly transmissible variant means more people are likely to get sick overall. As kids younger than 12 are not yet eligible to get vaccinated against COVID-19, they have a greater chance of getting infected, and therefore a higher risk of landing in the hospital.

"While severe outcomes of COVID-19 infection in pediatric populations continue to be relatively low compared to adults, the current exponential growth in hospitalizations is a very worrisome trend," John Brownstein, an epidemiologist at Boston Children's Hospital, told ABC News.

"As the remaining population ineligible for the vaccine, children will, unfortunately, be the main vectors of virus spread creating risk to both themselves and the rest of the population," he added.

The spike in pediatric cases is unfortunately timed right before the start of the school year. The CDC and AAP have urged that everyone in K-12 schools wear a mask indoors, regardless of their vaccination status. But some states have already banned mask mandates.

Florida and Texas are seeing the most kids hospitalized

Florida and Texas, two states that are seeing high rates of hospitalization due to COVID in the general population, have the greatest numbers of children under 18 hospitalized with the disease.

In Florida, a daily average of 54 kids under 18 were admitted to the hospital with COVID-19 between August 1 and 9, Insider's Dr. Catherine Schuster-Bruce previously reported.

In Texas, that figure reached 40 kids hospitalized per day during the same period. That's well above the national average of 5 children hospitalized with COVID-19 per day in any given state, if the state hospitalization rates were averaged together.

Calls for masks in schools

Both Florida and Texas have banned mask mandates in schools, contrary to recommendations from public health experts.

"As a physician, as a public health expert, it's deeply troubling that it seems we're letting politics get in the way of protecting our youth," said former US Surgeon General Jerome Adams, speaking about the bans on school mask mandates on CBS This Morning Tuesday.

"As a father, I quite frankly think it's unconscionable."