New Intensity to Debate Over Autism Cause
Parents and Researchers Grapple With Claims That Autism Is Linked to Thimerosal in Vaccines
"When we first heard the IOM committee was meeting, we said the meeting
was premature," Safe Minds' Bernard tells WebMD. "We told them to wait,
that more research is coming out. They ignored us. They went ahead and had
their meeting and missed a lot of evidence."
WebMD asked committee chairwoman Marie C. McCormick, MD, ScD, to comment.
McCormick is professor of maternal and child health at Harvard School of Public
"We had to make two kinds of assessments," McCormick tells WebMD.
"One was, did we see any evidence thimerosal was associated with autism. We
had five epidemiologic studies. None were perfect. But all pointed in the same
direction of no association."
Those five studies included five observational studies, using different
methods, looking for an association between autism and vaccination in Sweden,
Denmark, the U.S., and the U.K. None was found. Autism rates continued to rise
even after thimerosal was removed from vaccines.
Each of the studies had flaws. But they weren't nearly as flawed as Kennedy
suggests, says IOM spokeswoman Christine Stencel.
"The IOM committee certainly knew of these issues and found the studies
were relevant, that they were well designed, and that their data are
valid," Stencel says.
But what of the "truckloads" of studies to which Kennedy points?
"We looked at basic science and asked if there was any indication of how
thimerosal could cause autism," McCormick says. "We looked at over 200
scientific articles, and the evidence linking thimerosal to autism is purely
theoretical at best."
This does not satisfy Bernard. She doesn't think the evidence proves
thimerosal causes autism. But she does think the evidence points in that
direction. If researchers don't follow up, she fears, valuable time will be
"If you assume that there is a connection between mercury exposure and
an outcome of autism, then by studying what mercury does, you will come a lot
closer to learning how to treat these kids," Bernard says. "And if you
find a role for mercury, we can do a lot more in terms of prevention. You can't
just have effective treatment -- in today's science -- without understanding
the root cause."
Final Answer Coming Soon
Nearly everyone soon expects the controversy to end. One reason is that the
CDC is planning a massive, definitive study.
The other reason is that very soon, all the kids who got thimerosal in
vaccines will have reached the ages when autism should appear -- or not. If
there's no big drop in autism rates, thimerosal won't be much of an issue.
Still at issue, however, is the very real threat of mercury poisoning from
the environment -- a threat the world has only begun to deal with.
Advice for Parents