Nearly 72,000 children in the U.S. tested positive for COVID-19 last week, a massive jump from the approximately 39,000 cases among kids one week earlier, according to a new report from the American Academy of Pediatrics and the Children’s Hospital Association.

Children represented 19% of all COVID-19 cases for the week ending July 29.

Severe illness due to COVID-19 remains "uncommon" among children, the two organizations wrote in the report. According to the nearly two dozen states that reported pediatric hospitalizations, 0.1% to 1.9% of all child COVID-19 cases resulted in hospitalization.

However, the two organizations warned that there is an urgent need to collect more data on long-term impacts of the pandemic on children, "including ways the virus may harm the long-term physical health of infected children, as well as its emotional and mental health effects."

-ABC News’ Arielle Mitropoulos

According to federal data, nearly 56,000 patients are now hospitalized with COVID-19 across the U.S., marking the highest number of patients receiving care since February.

Ninety-one percent of Americans are now living in high (a seven-day new case rate ≥100) or substantial (a seven-day new case rate between 50-99.99) community transmission in the last week.

Seven states -- Alabama, Arkansas, Arizona, Delaware, Florida, Louisiana and South Carolina -- have high or substantial community transmission in every county.

Louisiana, Arkansas, Florida, Missouri, and Alabama currently have the nation's highest case rates, followed by Mississippi, Texas, and Oklahoma.

-ABC News’ Arielle Mitropoulos

In Texas, the demand for vaccines is skyrocketing. The number of daily doses has jumped from about 44,000 (just after the 4th of July) to 73,000 as of Monday, said Chris Van Duesen, spokesperson for the state’s Department of State Health Services.

National Institutes of Health director Francis Collins told CNN Tuesday the data is "tipping" toward showing how the delta variant is more serious for children than past variants.

Collins listed studies from Singapore, Scotland and Canada that "certainly tilts the balance in that direction" but made clear that more data is needed.

Collins also added that part of the reason the U.S. is seeing more children in hospitals is because they're part of the unvaccinated population and he doesn't want to "overstate the confidence."

-ABC News’ Cheyenne Haslett

A real-world study of South African health care workers found that the single-shot Johnson & Johnson vaccine was highly effective against the delta and beta variants, according to the South African Medical Research Council, which presented the results Friday.

The vaccine was between 91% and 96% effective against death, according the study, which included more than 477,000 health care workers. J&J showed stronger protection against the delta variant, now dominant in the United States and South Africa, than it showed against the beta variant.

"The data reported today by South African investigators show that a single shot can protect against death due to COVID-19 in the most challenging epidemiologic setting: A massive delta surge in Africa," said Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center, who helped invent the J&J shot but was not directly involved in the South Africa study.

While the results have not yet been published in a peer-reviewed journal, they may serve as a reassuring data point as the delta variant sweeps the U.S.

Glenda Gray, president and CEO of the South African Medical Research Council, who led the study, said at the Friday press conference that the J&J vaccine showed good durability, an indication that there's no need for booster shots just yet.

-ABC News' Sony Salzman.