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

Kennedy has been criticized for making false medical claims. He has also vowed to purge the U.S. Food and Drug Administration.

Shares of prominent vaccine makers plunged Thursday after President-elect Donald Trump announced his pick of Robert F. Kennedy Jr. to be the next secretary of the Department of Health and Human Services.