Vaccine stocks have struggled since RFK Jr.'s appointment to health secretary, with Moderna and Pfizer seeing the deepest losses.

President-elect Donald Trump said he’s tapping Robert F. Kennedy Jr. to run the Department of Health and Human Services, a move that would elevate a prominent vaccine skeptic and pharmaceutical industry critic to a top role on federal health policy.

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