Pfizer's stock dropped 4.3 percent while Moderna's fell 3.1 percent and Novavax saw a 2.8 percent dip in its stock Friday morning.

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

Shares in global vaccine makers and drugmakers fell on Friday after U.S. President-elect Donald Trump picked Robert F. Kennedy Jr., who has previously spread misinformation on vaccines, to lead the Department of Health and Human Services (HHS).