Two of the U.S. Food and Drug Administration's top vaccine regulators plan to leave the agency in the next several months amid a reported power struggle with the White House over COVID-19 booster shots. 

Dr. Marion Gruber, director of the FDA's Office of Vaccines Research and Review, plans to step down on October 31 and her top deputy Dr. Philip Krause also plans to leave the FDA in November, according to a department memo seen by EndPoints News.

Gruber played a key role in approving COVID-19 vaccines for the public, but her departure comes amid reports that FDA officials are frustrated with the White House for announcing booster shots before regulators formally approve them.

President Joe Biden has vowed to begin offering booster shots to the general public on September 20, a move that many health experts view as politicized and premature in coming before the FDA issues a formal recommendation.

In the US, the first courses of COVID vaccines from Johnson & Johnson and Moderna have emergency use authorization from the FDA, while the Pfizer vaccine's two-dose initial course has full approval. But the FDA has yet to rule on widespread booster doses.

In a joint statement last month, Biden's top health advisors called for a booster course of an additional Pfizer or Moderna shot for anyone who had received any of the three vaccines now in use, starting eight months after the initial dose.

'We have developed a plan to begin offering these booster shots this fall subject to FDA conducting an independent evaluation and determination of the safety and effectiveness,' the statement said.