Senate Democrats want more details on the reassignment of top vaccine expert Dr. Rick Bright amid the coronavirus pandemic.
Four committees sent a letter Thursday demanding answers from Health and Human Services Secretary Alex Azar.
The letter says, "Our response to this crisis cannot be steady if its leadership is being constantly shuffled and if experts are being constrained or removed when they insist on following the science and sticking to the facts."
Bright was leading the development and purchasing of vaccines. He says he was removed from his post after refusing to promote hydroxychloroquine as a treatment for coronavirus. President Donald Trump has often called the drug a success even though recent studies found it has no benefit to recovery.
The letter asks Azar to respond to a number of inquiries by May 13.