Several moves suggest Health Secretary Robert F. Kennedy Jr. could revive his campaign to question the safety and effectiveness of the shots after the midterm elections.

Over two dizzying days in Washington this week, Health Secretary Robert F. Kennedy Jr. appeared to change his tune on vaccines. The nation’s loudest vaccine skeptic conceded that the measles vaccine was safe and effective for “most people” and put forth a slate of doctors who support vaccines to lead the Centers for Disease Control and Prevention.

But whether those shifts are merely cosmetic, or will produce real policy change, is an open question.

Mr. Kennedy is still surrounded by allies, notably the lawyer Aaron Siri, who are pushing him to roll back existing vaccine policy. Last week, apparently in response to a petition by Mr. Siri, the C.D.C. published a new charter for a vaccine advisory committee that enables Mr. Kennedy to sidestep a federal court ruling barring changes to the panel.