Why Are Vaccination Rates Lower Among Kids With ASD?

Hi. My name is Paul Offit, and I'm talking to you today from the Vaccine Education Center at The Children's Hospital of Philadelphia. I want to talk about a paper that was recently published in JAMA Pediatrics^[1]. The study was performed by researchers at the Kaiser Permanente healthcare system in collaboration with researchers at the Centers for Disease Control and Prevention. At issue were vaccination rates among children with autism spectrum disorder (ASD).

These researchers looked at 3729 children with ASD and compared them with 592,907 children without the disorder. They found that children with ASD were statistically significantly less likely to be vaccinated than those without the disorder. They also found that the younger children whose older siblings had ASD were less likely to be vaccinated than younger children whose older siblings did not have ASD.

Why is this happening? The notion that vaccines cause autism was born in 1998, when Andrew Wakefield and colleagues published a paper in The Lancet^[2] claiming that the measles, mumps, rubella (MMR) vaccine caused autism. In the 20 years since then, 17 studies^{[3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]} have shown that the MMR vaccine does not cause autism.

Also in the late 1990s, the notion was born that thimerosal (an ethylmercury-containing preservative in vaccines) could cause autism. That too, has been refuted with seven studies^{[20,21,22,23,24,25,26]} that show that thimerosal, at the level contained in vaccines, does not increase the risk for neurodevelopmental delays, including autism.

Then the hypothesis shifted again, to the notion that children were just getting too many vaccines too early in life. That, too, has been examined in two studies^[27,28] that showed that this was not a problem in terms of increasing the risk for autism.

Why do these fears persist? I think that there are a lot of reasons for that. One of them is that we don't know the clear cause or causes of autism. We don't have a cure for autism, so this just sort of hangs out there. You could make an analogy to diabetes in the late 1800s, when no one really knew what caused it, and there were a lot of crazy cures proffered by charlatans. In 1921, Banting and Beck discovered insulin, and all those crazy cures and crazy ideas about what caused diabetes disappeared.

What we have are parents who are choosing not to vaccinate children with ASD, which will only put them at risk for infectious diseases and does not in any sense lessen their symptoms of ASD. Certainly, for the younger siblings who aren't being vaccinated, it doesn't lower their risk of developing this disorder; it just puts them at risk for vaccine-preventable diseases. All these children are being put in harm's way, with potentially tragic consequences.

We have to continue to do the best we can to educate parents that these are not good choices. Thank you.