For decades, scientific consensus has held that vaccines do not cause autism, but KFF polling and media monitoring show that uncertainty remains widespread. Recent changes to the CDC’s website language falsely asserting that a link between vaccines and autism cannot be ruled out may introduce ambiguity that online narratives can exploit.
Most people are not firmly entrenched in false beliefs but remain uncertain. KFF Health Information and Trust tracking polls find high exposure to the autism myth and low certainty about its accuracy. As of April, 63% of adults and 61% of parents had heard the claim that MMR vaccines have been proven to cause autism, but fewer than 5% say it is “definitely true.” Most fall into the “muddled middle,” saying this claim is “probably true” or “probably false.” This uncertainty matters: the same poll found parents who endorse false claims are twice as likely to delay or skip vaccines compared to those who view these claims as false. Partisan and demographic divides exist, with Republican parents and those without a college degree more likely to express doubt or lean toward believing the claim.
After news of the CDC’s language change broke, there was a surge of online reactions on social media that both celebrated and criticized the change, indicating persistent mixed beliefs among the public. Ongoing media monitoring suggests that when official guidance changes, online narratives frame it as proof that prior statements were “lies,” potentially contributing to uncertainty and deepening skepticism.
Taken together, these findings illustrate how uncertainty about vaccines and autism persists even after decades of research, and how shifts in official language can interact with that uncertainty. Polling shows most people are not firmly committed to false beliefs but remain unsure. At the same time, media monitoring suggests that changes in guidance often become focal points for online narratives framing prior statements as misleading. This combination of high exposure and low certainty may pose a challenge for communicators when scientific consensus meets changing institutional messaging, and possibly contribute to fewer children getting vaccinated against deadly childhood diseases.