When Donald Trump made an alliance with Robert F. Kennedy, Jr., he brought vaccine skepticism and the debunked link between vaccines and autism into the center of the MAGA agenda. Though the scientific establishment has long disproven that link, as many as one in four Americans today believe that vaccines may cause autism. In April, Kennedy, now the Secretary of Health and Human Services, shocked the medical community and families across the country when he said that his agency would uncover the cause of autism—the subject of decades of research—once and for all. That news came even as Kennedy oversees drastic cuts to critical medical research of all kinds. Dr. Alycia Halladay, the chief science officer of the Autism Science Foundation, talks with David Remnick about the initiative, and the problems with focussing on environmental factors such as vaccines or mold. She also discusses why debunked claims and misinformation have such a powerful hold on parents. “You will do anything to help your child, so if it means a bleach enema”—referring to one extremely poisonous and falsely touted treatment—“and you think that’s going to help them, you’ll do it. It’s not because these people don’t love their children. It’s because they’re desperate.”