Robert F. Kennedy Jr. in Phoenix on Aug. 23, 2024. Thomas Machowicz | Reuters Shares of vaccine makers fell Thursday as President-elect Donald Trump nominated Robert F. Kennedy Jr., a prominent vaccine skeptic, to lead the Department of Health and Human Services.  The stocks fell in the final hour of trading as reports emerged about Trump’s expected pick. Moderna‘s stock closed more than 5% lower on Thursday, shares of Novavax