The White House has appointed Jim O’Neill, deputy secretary of Health and Human Services and a longtime aide to HHS Secretary Robert F. Kennedy Jr., as acting director of the Centers for Disease Control and Prevention, according to administration officials. The move was first reported by the Washington Post on 28 August. O’Neill, a former biotech investor who joined the administration in June, will take the helm of the $9.2 billion public-health agency immediately while continuing in his current HHS post. He previously worked on pandemic preparedness and FDA policy during the George W. Bush administration and has publicly supported vaccines, even while criticizing parts of the Biden-era Covid-19 rollout. His elevation follows the abrupt firing of CDC Director Susan Monarez on 27 August after a clash with Kennedy over proposed limits on Covid-19 vaccinations. Monarez, the first Senate-confirmed CDC chief, is contesting her removal. In the wake of her ouster, three senior CDC leaders—Dr. Debra Houry, Dr. Daniel Jernigan and Dr. Demetre Daskalakis—resigned, citing concerns that scientific decision-making was being undermined. The leadership shake-up has drawn bipartisan calls for congressional oversight as the CDC’s vaccine advisory panel, recently reshaped by HHS, prepares to issue recommendations next month. While O’Neill’s appointment is temporary, any permanent director will require Senate confirmation, setting up another potential confrontation over the agency’s direction.