Andrew M. Seaman has confirmation of something we already knew, just in case someone missed the memo:

The measles, mumps and rubella (MMR) vaccine is not linked to development of autism spectrum disorders, even among children considered to be at risk, a large new study finds.

Among nearly 100,000 children, receipt of the MMR vaccine did not increase the risk for autism spectrum disorder (ASD), regardless of whether kids were at higher risk because an older sibling already had the condition, researchers write in JAMA.

“Even for children who are high-risk, the vaccine does not play a role,” said lead author Dr. Anjali Jain of healthcare consulting firm The Lewin Group in Falls Church, Virginia. “We don’t know what does unfortunately, but it’s not the MMR vaccine.”


For parents who delay or refuse vaccines because an older child has been diagnosed with autism (even though it is well-known that vaccines don’t cause autism), the study should be reassuring. Amy Norton spoke with autism researcher Bryan King, who says that autism results from a “triple hit” — genes, an environmental trigger, and timing during critical, prenatal brain development. Whatever that environmental trigger is, what this study makes clear is that it’s not MMR vaccine. Dr. King points to the direction of future research:

“Everyone believes there have to be environmental factors contributing to the exponential rise we’ve seen in ASDs,” he said. “But we don’t understand what those factors are yet.”

Researchers are finding clues, though. And more and more, they suspect that prenatal brain development is the critical period, King said.

He pointed to one study published just last week. There, researchers found that among more than 322,000 children, the risk of autism was elevated among children whose mothers had pregnancy-related diabetes in the first or second trimester.

It’s not yet clear what that means, King stressed. But, he noted, some of the genes linked to autism are also involved in regulating insulin — the blood-sugar-controlling hormone that goes awry in diabetes.

According to King, studies like that are opening new ideas on the potential environmental risk factors for autism — even as others are “closing the door” on the MMR theory.


Speaking of that “MMR theory”: Don’t let the door hit you on your way out!