Florida Gov. Ron DeSantis' school mask mandate ban was reinstated by an appeals court Friday.

This overrules a Tallahassee judge's decision on Wednesday to lift the stay, preventing the state from enforcing the ban. (The appeals court still needs to rule on the legality of the order, but the reinstatement of the stay means that until then, the state can continue sanctioning school districts.)

DeSantis responded on Twitter, "I will continue to fight for parents’ rights."

DeSantis has struggled to rein in the state's largest school systems as they implement mask mandates in defiance of state law. At least 13 districts, including Florida's six largest, have mask requirements in place. The Florida Department of Education has threatened to withhold the salaries of school board members in most of these districts and has begun doing so in at least two cases.

-ABC News' Will McDuffie

In hard-hit Kentucky, over 300 more National Guard members will be sent to help at 21 strained hospitals, Gov. Andy Beshear said.

Kentucky's positivity rate was above 14% Thursday as the state set new records for hospitalizations and patients on ventilators, the governor said.

"In the past month, ventilator use at hospitals has nearly tripled due to the surge from the delta variant," Beshear tweeted. "Our hospital situation has never been more dire in my lifetime than it is right now. We cannot handle more sick individuals."

-ABC News' Will Gretsky

The unvaccinated "are 10 times more likely to be hospitalized and 11 times more likely to die," CDC director Rochelle Walensky said at Friday's White House COVID briefing.

Three new studies from the CDC show vaccines still dramatically reduce the risk of hospitalization and death amid the delta surge. 

A study of U.S. veterans fully vaccinated with Pfizer and Moderna found no real change in vaccine effectiveness against hospitalization pre-delta to post-delta. A second study of all three vaccines across nine states found vaccine effectiveness against hospitalization was 86% for all age groups. A third study of all three vaccines across 13 jurisdictions found vaccines performed roughly equally well protecting against hospitalization and death during the delta surge compared to pre-delta.

Across the studies, vaccines remained 86-87% effective against preventing hospitalizations.

But effectiveness dropped more for people ages 65 and older in recent months compared to before delta, likely due a combination of vaccine effectiveness fading over time and the slight impact of the delta variant on vaccine efficacy.

Vaccines are losing some of their effectiveness when it comes to preventing mild infections among the vaccinated.

-ABC News' Sony Salzman

While awaiting Pfizer trial data for kids ages 5 to 11, the Food and Drug Administration is vowing not to cut corners.

The FDA said, "it’s critical that thorough and robust clinical trials of adequate size are completed to evaluate the safety and the immune response."

"Children are not small adults -- and issues that may be addressed in pediatric vaccine trials can include whether there is a need for different doses or different strength formulations of vaccines already used for adults," the FDA said.

When the FDA receives a completed emergency use authorization request, "the agency will carefully, thoroughly and independently examine the data to evaluate benefits and risks and be prepared to complete its review as quickly as possible, likely in a matter of weeks rather than months."

"However, the agency’s ability to review these submissions rapidly will depend in part on the quality and timeliness of the submissions by manufacturers," the FDA added.

-ABC News' Anne Flaherty