Long before the COVID-19 pandemic, Robert F. Kennedy Jr. was building up a following with his anti-vaccine nonprofit group, Children’s Health Defense, and becoming one of the world’s most influential spreaders of fear and distrust around vaccines.

President-elect Donald Trump had touted Kennedy as a potential pick for the role of health secretary in the run up to his election victory, even if senior members of his campaign ruled out Kennedy having an official role.

The nearly $2 trillion agency administers health-insurance programs for millions of Americans, approves medications and oversees vaccine safety.