When the week began, several senior positions at the U.S. Department of Health and Human Services were already sitting empty. There was no Senate-confirmed U.S. surgeon general. The head of the National Institutes of Health was doubling as the acting head of the U.S. Centers for Disease Control and Prevention. The Food and Drug Administration lacked a permanent vaccine chief after that official was ousted for a second time in a year. Then on Tuesday Dr. Marty Makary resigned as head of the FDA , leaving another major health agency with only an acting commissioner. Makary's departure widens a leadership gap that has plagued HHS throughout Health Secretary Robert F. Kennedy Jr.’s tenure. Across a vast and multilayered government, in which many leadership positions must be confirmed by a Senate that shares only a narrow partisan majority with the administration, it’s typical for some roles to remain unfilled or be occupied by interim leaders.…