Do Vaccines Cause Autism?


>>Hi, my name’s Paul Offit. I’m talking to
you today from the Vaccine Education Center here at The Children’s Hospital of Philadelphia.
Probably the question that’s most been entertained, I guess, regarding vaccines by the media,
is the question about whether or not vaccines could cause autism. And this notion was born,
really, in the late 1990s, associated with a publication of a paper in a British Journal
called The Lancet, claiming that the combination measles, mumps, rubella, or MMR vaccine caused
autism. Now, that was … it raised the question.
You can argue that what this paper did, it raised the question. You can argue it’s a
reasonable question. I mean for some parents, “My child was fine. They got a vaccine, then
a month, or two, or three later, they started to develop signs and symptoms of autism. Could
the vaccine have done it?” This is an answerable question. The way you
answer it is you look at large numbers of children who either did or didn’t get the
measles, mumps, rubella vaccine to see if you are at greater risk of having autism if
you got the vaccine and if you didn’t. And there have been at least 12 studies now involving
hundreds and hundreds of thousands of children on several continents that have found the
exact same thing. Most recently there was a study that was published
in the Journal of the American Medical Association. It involved a database of 91,000 children.
And what they did was they looked at younger children where the older child already had
autism. To see whether … if that younger child got vaccinated or didn’t get vaccinated,
whether the younger child, when vaccinated, was more likely to get autism. And an obviously
an at-risk child because the older child, the sibling, already had autism. And the answer
was no difference. Didn’t matter whether you vaccinated or didn’t vaccinate the younger
child, there was an equal risk of getting autism. So all you did by not giving that younger
sibling vaccines was increase their risk of getting vaccine-preventable diseases without
in any way decreasing their risk of getting autism. Then what happened is the hypothesis, if you
will, morphed to not that MMR vaccine caused autism, but that thimerosal, an ethylmercury-containing preservative in vaccines, caused autism. That was actually very easy to study. I mean, we
had taken thimerosal out of vaccines in our country by the year 2000, at least as given
to young child. There were Canadian provinces that used vaccines that contained thimerosal right
next to provinces that used the same vaccines that didn’t contain thimerosal. Western Europe
took thimerosal out of vaccines by 1991. So, it was very easy to do the kinds of studies
to see whether or not thimerosal had any impact on the development of autism. Or even subtle
signs of mercury poisoning for that matter. And there was no association. Then more recently this sort of the hypothesis
morphed again. Do children just get too many vaccines to soon and that causes autism. Now,
there’ve been a couple studies that have looked at that. Looking at children who got vaccines
according to the recommended schedule, compared to those whose parents had chosen to delay,
or withhold vaccines. And again, no difference in autism. So I think while we don’t know what the cause
or causes of autism is, I think what we can say with confidence is that vaccines aren’t
it. It’s probably the best studied of the environmental factors associated with the …
that people have been concerned about regarding autism. Thanks.

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