(Eric Lee | The New York Times) Secretary of Health and Human Services Robert F. Kennedy, Jr. leaves Speaker of the House Mike Johnson’s office at the U.S. Capitol in Washington, March 25, 2025. A steadfast figure in the anti-vaccine movement who has helped shape Health Secretary Robert F. Kennedy Jr.’s thinking on a possible link to autism has joined his department to work on a study examining the long-debunked theory, according to people familiar with the matter.