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 became one of the world’s most influential spreaders of fear and distrust around vaccines.

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

The choice will roil many public health experts after his years of touting debunked claims that vaccines cause autism.