For more than 20 years, the Centers for Disease Control and Prevention told the public that studies show no link between vaccines and autism. On Nov. 19, it revised its messaging, acknowledging that current evidence does not rule out a possible association. This was not an announcement of a newly discovered risk; it was a correction of an earlier claim that exceeded what the science had demonstrated. The CDC update to its website was a long-overdue correction of the messaging.
The reality of the research on autism and vaccines is clear. All the foundational studies on this topic — the ones cited to say that the science is settled — were designed to detect moderate to large increases in the risk of autism. None of them were designed to detect small increases, and by “small” think increases in autism risk of 5% to 20%.
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