MacNeil on Autism Causation

The NewsHour's MacNeil series takes on the issue of causation, including the vaccine controversy:

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ROBERT MACNEIL: One issue science considered settled for years won't go away: the parental belief that vaccines cause autism. Public health officials have steadily maintained there is no valid, scientific evidence of such a connection; all epidemiological studies have proved negative. But now, bowing to public opinion, the body that sets priorities in autism research, The Inter Agency Coordinating Committee, has recommended studies to determine whether small subgroups might be more susceptible to environmental exposures, including vaccines.

DR. GERALD FISHBACH: Despite many, many, many epidemiological studies, no evidence that current vaccines in their present form have triggered autism. There are two prevalent things going on here: vaccination and autism. But trying to correlate those two have failed to date.

DR. DAVID AMARAL: So I think it's pretty clear that, in general, vaccines are not the culprit. If you look at children that receive the standard childhood vaccines. If anything those children are at are at slightly less risk of having autism than children that aren't immunized. It's not to say, however, that there is a small subset of children who may be particularly vulnerable to vaccines if the child was ill, if the child had a precondition, like a mitochondrial defect. Vaccinations for those children actually may be the environmental factor that tipped them over the edge of autism. And I think it's -- it is incredibly important still to try and figure out what, if any, vulnerabilities in a small subset of children might make them at risk for having certain vaccinations.

DR. MARTHA HERBERT: I think it's possible that you could have a genetic subgroup. You also might have an immune subgroup. There are a variety of subgroups. But the problem with the population studies is they don't they aren't necessarily designed to have the statistical power to find subgroups like that if the subgroups are small.

DR. DAVID AMARAL: I think more importantly what the whole vaccine issue has done is has opened our eyes again to the idea that the immune system is an important component of autism.