COVID-19 updates: 345 children currently hospitalized with coronavirus in Texas

Peter Marks, the director of the Food and Drug Administration's Center for Biologics Evaluation and Research (CBER), announced the upcoming departure of two top vaccine regulators to his staff in an internal memo, which was obtained by ABC News.

Dr. Marion Gruber, director of the FDA's Office of Vaccines Research and Review (OVRR) and her deputy, Dr. Phil Krause, are set to leave the agency in October and November respectively, according to the memo.

Krause, who's been with the agency for over a decade, and Gruber, who has been with the FDA for over 30 years, were instrumental in the review and authorization of the three COVID-19 vaccines, the memo said.

The memo said that Gruber will be "retiring" and gave no other details about Krause's departure.

ABC News has reached out to both Gruber and Krause for comment. 

When reached for comment about their departure, an FDA spokesperson told ABC News the agency is "confident in the expertise and ability of our staff to continue our critical public health work, including evaluating COVID-19 vaccines."

Their departures come at a critical time for the vaccine review team. After facing pressure to move as fast as possible to get vaccines' full licensure done, the agency is now weighing booster shots for a wider pool of Americans.

The timing of the booster shot approval has been a bone of contention amongst federal agencies after the Biden administration announced the availability of booster shots would begin ahead of any ruling from the FDA or Centers for Disease Control and Prevention advisory groups.

-ABC News' Sasha Pezenik

Jacqueline Jackson, the wife of civil rights leader Rev. Jesse Jackson, is out of the ICU as both Jacksons continue to fight COVID-19, their family said.

"Our father remains at The Shirley Ryan AbilityLab where he is continuing to receive intensive occupational and physical therapy," their son, Jonathan Jackson, said in a statement Tuesday.

Jesse Jackson, who is 79 and has Parkinson's disease, was vaccinated, reported ABC Chicago station WLS.

"Our mother remains in the Northwestern Memorial Hospital and has been moved out of the ICU and back into her regular hospital room where she continues to receive oxygen," the statement said. "Both of our parents are continuing to receive excellent medical care and we thank God for the progress that both seem to be making."

The U.S. vaccination rate per day is now nearly double than it was in mid-July, according to the White House.

"Back in mid-July we were averaging 500,000 vaccinations per day. Today, we’re averaging 900,000," White House COVID response coordinator Jeff Zients told reporters Tuesday. "Last week we got over 6 million shots, the biggest weekly total since July 5."

The increase in vaccinations comes amid fear about the rapidly spreading delta variant. 

The delta variant, which is more transmissible, has also been part of the conversation around booster shots of the mRNA and J&J vaccines. The Biden administration said Americans would need a third shot eight months after their second because of waning immunity.

The Biden administration is standing by its decision to call for vaccine boosters beginning Sept. 20 despite questions about whether there's enough data and the unusual process of announcing a plan before the FDA has evaluated the data and made a recommendation.

-ABC News' Cheyenne Haslett

Idaho only has four adult ICU beds available in the state, Gov. Brad Little said Tuesday.

The governor said he toured a nearly-full ICU in Boise where everyone was unvaccinated.

"What I saw was heartbreaking," Little said at a news conference. "I was told the average age of the patients was 43. All of them were struggling to breathe and most were only breathing with the help of a machine. Doctors, nurses and associated medical staff are exhausted."

The governor said up to 370 additional staff, including up to 150 National Guardsmen, will be deployed to help short-staffed hospitals manage the surge.