Education Secretary Miguel Cardona told Florida superintendents in a new letter that he’ll stand with any school that defies Gov. Ron DeSantis by implementing a mask mandate.

He also spelled out how schools can use federal COVID-19 relief dollars, already appropriated by Congress, "to support any activity necessary to maintain operations," including reimbursing pay of education officials withheld by the governor. DeSantis later admitted he couldn't slash superintendents' pay since it is a local matter, but implausibly called on superintendents to slash their own pay if they defied his ban on mask mandates.

"Several school districts in Florida have already moved to adopt universal masking policies despite the State’s prohibition, and I want you to know that the U.S. Department of Education stands with you," he wrote. "Your decisions are vital to safely reopen schools and maintain safe in-person instruction, and they are undoubtedly in the best interest of your students."

He later added, "In these unprecedented and difficult times, the leadership and courage that you are showing will make a difference in the lives of the students whom you serve."

-ABC News' Anne Flaherty and Sophie Tatum

Hours after the Centers for Disease Control and Prevention officially recommended a third dose of an mRNA vaccine for immunocompromised Americans, both Walgreens and CVS said Friday they will be able to administer third doses of the Pfizer and Moderna vaccines to eligible patients.

Walgreens said walk-ins are welcome now at select locations, while CVS said appointments will be available starting Saturday.

Both companies said patients should be prepared to prove their eligibility for a third dose.

-ABC News' Sasha Pezenik

Oregon Gov. Kate Brown said Friday she is deploying up to 1,500 members of the National Guard to help hospitals throughout the state "overstretched by patients during the delta surge."

"I cannot emphasize enough the seriousness of this crisis for all Oregonians, especially those who might need emergency or intensive care," Brown said in a video message. "When our hospitals are filled with COVID-19 patients, there may not be a room for someone needing care after a car crash or a heart attack or other emergency situation."

As of Friday morning, there were 733 people hospitalized with "severe cases" of COVID-19, including 185 patients in the intensive care unit, Brown said.

The Oregon Health Authority and the Oregon Department of Human Services are also working to provide support to hospitals, and Brown said she is requesting FEMA support.

In the meantime, the governor urged people to wear a mask while in public and get vaccinated if they haven't yet.

The American College of Physicians said Friday that masks should be required in all schools "as part of a comprehensive effort to reduce the spread of COVID-19."

The statement follows similar recommendations from the American Association of Pediatrics and the Centers for Disease Control and Prevention, and comes as some school districts have been defying bans on masks mandates in states including Texas and Florida.

"Masks are a key public health tool in keeping everyone in our school communities safe," ACP President Dr. George Abraham said in a statement. “Especially with such a large segment of our schools’ populations unable to yet access COVID-19 vaccines, masks remain a necessity in our fight to control the COVID-19 pandemic."

The ACP is the largest medical specialty society in the U.S., with over 161,000 internal medicine members.