(Bloomberg) -- Two key vaccine officials are preparing to step down from the U.S. Food and Drug Administration, which raced to clear Covid shots to fight the pandemic and is now considering President Joe Biden’s booster plan.

Marion Gruber, head of the regulator’s Office of Vaccines Research and Review, plans to retire on Oct. 31 and Philip Krause, deputy director for the FDA’s Center for Biologics Evaluation and Research, will be leaving the following month, according to an email to staff that was viewed by Bloomberg. 

U.S. health officials have been working to evaluate Covid vaccines and treatments at top speed, with shots from Moderna Inc., Johnson & Johnson and the partnership of Pfizer Inc. and BioNTech SE cleared in record time. Now the agency is charged with considering the administration’s booster program, which is set to roll out additional shots for most U.S. vaccinated adults Sept. 20.

“We are confident in the expertise and ability of our staff to continue our critical public health work, including evaluating COVID-19 vaccines,” FDA spokesperson Stephanie Caccomo said in a statement. 

The search for the next office director will begin imminently, Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in the email to staff. He will serve as acting office director of the Office of Vaccine Research and Review.

The departures were reported earlier by Biocentury. 

©2021 Bloomberg L.P.