The Trump administration has fired the two leaders of an influential health group that determines when insurance must provide free preventive care, like mammograms and colonoscopies, for millions of Americans.

In letters dated May 11, Health Secretary Robert F. Kennedy Jr. notified the two doctors who chaired the U.S. Preventive Services Task Force that he was terminating their appointments immediately, before the end of their multiyear terms.

The Department of Health and Human Services already had largely sidelined the task force, indefinitely postponing scheduled public meetings over the past year and thus leaving some long-expected updates on cervical cancer screenings and other topics in limbo.

The panel, first created in the 1980s, is composed of experts who scrutinize the latest evidence behind a wide array of disease prevention tools, such as depression screenings ad the use of statins to prevent heart attacks. The panel updates guidelines with letter grades showing the strength of the science. Under the Affordable Care Act, most insurance plans must cover preventive services given an “A” or “B” grade without requiring a co-pay.

Kennedy’s letters don’t make clear why he ousted Drs. John Wong and Esa Davis from the panel. He wrote that their “leadership, contributions and expertise” have advanced the task force’s work “to improve the health of Americans” and encouraged them to reapply. He said he was reviewing task force appointments “to ensure clarity, continuity and confidence” in HHS oversight.

The letters were first reported by The New York Times. An HHS spokesman didn’t respond to questions about why the two were fired.

Kennedy told lawmakers last month that he was reforming the task force, calling it “lackadaisical,” so that it would meet more frequently and “have, for the first time, transparency.” The panel holds public meetings, opens its draft guidelines to public comment before finalizing them, and publishes the scientific evidence behind them.

Some health advocates had worried that Kennedy was preparing to replace the expert panel with less experienced political appointees, like he had done with a critical vaccine advisory committee. Over the past year, the task force wasn’t allowed to publish its final update to the cervical cancer screening guideline or take steps to update recommendations about maternal depression, said former task force chairman Dr. Michael Silverstein, a pediatrician.

“This is a level of government intrusion into scientific processes that I’ve not experienced in my 10 years on the task force,” he said.

The panel has staggered terms so that normally health secretaries can regularly appoint new members, making their mark on the task force without upending it, said Aaron Carroll of the nonpartisan healthy policy group AcademyHealth.