Health care: September 2010 Archives
Another study showing that thimerosal—the ethylmercury-containing vaccine preservative—does not increase the risk of autism hardly seems necessary. For the rational majority, who are inclined to believe the results of credibly authored reports, there are at least 5 studies that fail to show a link between pre- or postnatal exposure to thimerosal and poor neuropsychologic outcomes or autism. (Moreover autism rates continue to rise despite the removal of thimerosal from childhood vaccines in 1999.) For the small group of irrational and very vocal citizens who maintain a causal connection between thimerosal and autism, no amount of negative data appears sufficient.
Nevertheless the results of a new case-control study, published in Pediatrics, are now available. And not only do they deny an increased risk of autism with thimerosal exposure (either in utero or later); they actually indicate that postnatal exposure to thimerosal significantly reduces the risk of autism—by about 40%. The authors (perhaps wisely) avoided speculating as to the reason for the reduced risk, however.
The case-control data were collected from children* enrolled continuously in 3 managed care organizations that participate in the CDC's Vaccine Safety Datalink. The study methods are distinctive in that the authors, in addition to mining electronic databases and medical charts, validated autism diagnoses in person and conducted parent interviews.
* 256 with autism spectrum disorder and 752 controls matched for birth year, sex, and MCO.