Under Secretary Robert F. Kennedy Jr.’s leadership at the Department of Health and Human Services, the Centers for Disease Control and Prevention softened its longstanding position in November 2025, shifting from “vaccines do not cause autism” to stating the evidence isn’t strong enough to completely rule out a possible link, citing several older studies on aluminum adjuvants and vaccine timing.

Months later, key studies used to justify that change were retracted by journals for methodological flaws, sparking backlash from Kennedy, who demanded greater transparency, while the CDC’s revised stance faced fresh scrutiny.

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