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    Autism-Vaccine Link: Evidence Doesn't Dispel Doubts

    Many major medical groups say vaccines don't cause autism. Many parents say they do. So who's right?

    Vaccine-Autism Disconnect: Complex Science continued...

    But those who take issue with the scientific consensus that vaccines have very little to do with autism focus on research that seems to support their opinions. In particular, they point to the work done by Mark Geier, MD, PhD, a former researcher at the National Institutes of Health, and his son, David Geier, whose studies did show a strong link between autism and vaccines.

    So who's right? An Institute of Medicine panel reviewed all of the evidence on vaccines and autism in 2004. But the reviewers excluded the Geier studies, finding them "uninterpretable." The AAP issued a statement explaining how the Geiers were probably wrong, listing 15 critical errors or omissions in just one of their studies.

    Still, some activists believe that authorities are suppressing this evidence because it's inconvenient, and the Geiers have never backed off from their conclusions. But experts say the basic flaws of their studies are glaringly obvious.

    Marie McCormick, MD, a professor at the Harvard School of Public Health, oversaw the committee that conducted the 2004 IOM vaccine safety review and extensively reviewed their work. To begin with, she says, the Geirs used inappropriate data sources for their studies.

    One study was based upon case reports in the CDC's system for tracking vaccine side effects. Those reports can alert researchers to issues that deserve study. But they're a far cry from the sort of evidence scientists need to prove something.

    In addition, when researchers try to prove cause and effect, they use samples that reflect the general population. So using only data about people who got sick from vaccines isn't generalizable.

    Other studies done by the Geiers also had flaws, McCormick says. In one of them, the Geiers estimated a rate of autism in different groups of U.S. children based upon case records for government-sponsored special education programs. But because eligibility requirements vary from state to state, it's unlikely that the special-ed rolls accurately reflect a real rate of autism.

    What's more, the Geiers made major errors with their calculations. "They didn't understand how to analyze the data," McCormick says. Such statistical flaws are fatal, but all that goes over the heads of many people. "If you stand up in front of an audience and explain that, you are going to look like a nerd," McCormick says.

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