Robert F. Kennedy Jr.’s long-shot presidential campaign has a new communications director — prominent anti-vaccine activist Del Bigtree. In a letter to supporters, Bigtree called the appointment “my greatest opportunity to date.” In speeches and interviews, Kennedy has credited the anti-vaccine movement with powering his candidacy and vowed as president to halt research into infectious diseases and use the power of the attorney general to threaten editors of medical journals over publishing research on Covid treatments and vaccines. Bigtree is the executive director of the Informed Consent Action Network (ICAN), the country’s second best-funded anti-vaccine organization, after Children’s Health Defense,...