On November 19, 2025, Health and Human Services Secretary RFK Jr. changed a section on the CDC website titled “Vaccines and Autism.” The website now includes the usual bogus claims about vaccines and autism that RFK Jr. has been promoting for the last 20 years. But the first statement is the most telling.

The website now states: “The claim ‘vaccines do not cause autism’ is not an evidence-based claim because studies have not ruled out the possibility that infant vaccines cause autism.” This statement takes advantage of a technicality in the scientific method that anti-vaccine activists have been using for years to promote fear of vaccines despite overwhelming evidence to the contrary.

Here’s how the scientific method works: Researchers interested in determining, for example, whether th

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