President-elect Donald Trump said Thursday he has picked Robert F. Kennedy Jr., a vaccine skeptic, to lead the Department of Health and Human Services, he announced in a social media post.

Trump said that Kennedy will “restore” the agencies under HHS “to the traditions of Gold Standard Scientific Research, and beacons of Transparency, to end the Chronic Disease epidemic, and to Make America Great and Healthy Again!”

Kennedy has been an anti-vaccine activist and founded the Children’s Health Defense, a prominent anti-vaccine nonprofit that has campaigned against immunizations and other public health measures like water fluoridation. Medical experts expressed concerns about a rise in medical misinformation through Kennedy’s candidacy. Notably, Kennedy has falsely claimed that childhood vaccines cause autism, despite the retraction of the study that originally suggested this link and numerous subsequent high-quality studies disproving this theory.