The White House has appointed Jim O’Neill, the deputy secretary of Health and Human Services and a principal aide to Health Secretary Robert F. Kennedy Jr., as acting director of the Centers for Disease Control and Prevention, according to administration officials cited by the Washington Post and other outlets on 28 August. O’Neill replaces Susan Monarez, who was dismissed less than a month after taking the helm of the $9.2 billion agency amid an escalating dispute with the administration over vaccine policy. Monarez’s removal triggered the resignations of three senior CDC leaders—Debra Houry, Demetre Daskalakis and Daniel Jernigan—deepening the leadership vacuum at the Atlanta-based public-health agency. A former biotech investor and George W. Bush–era HHS official, O’Neill has publicly described himself as “strongly pro-vaccine” while criticizing elements of the previous administration’s COVID-19 response. He assumes control as lawmakers call for oversight of the CDC’s direction and as a reshaped Advisory Committee on Immunization Practices prepares to issue new immunization recommendations in September.