Disconnect. new cases of autism continued to rise after a vaccine preservative has been removed.
Two new studies cast more doubt on the theory that a mercury-based preservative in vaccines causes autism. Called thimerosal, the preservative has been eliminated in many industrialized countries, but is still used in the developing world. The new findings "provide additional data, extremely reassuring," says William Schaffner of Vanderbilt University School of Medicine in Nashville, Tennessee.
In 1999, attorneys parent groups such as Safe Minds suggested that thimerosal may explain the increasing incidence of autism, who often appears at about the same time as 2 years get a series of booster doses. many scientists were skeptical, but in 01 an Institute medicine panel concluded that there was not enough evidence to dismiss or accept the link.
Now the first large epidemiological studies weigh. People come from Denmark, which eliminated thimerosal from vaccines child in 1992 a team led by Kreesten Madsen epidemiology of the Danish science Centre in Aarhus said that if thimerosal were a major cause of autism, the incidence is expected to decline once it has removed. But he continued to soar after the phaseout 1992, according to a report in the September issue of the journal Pediatrics . A similar pattern emerges of health statistics in Sweden, where the total mercury in childhood vaccines began to decline in the late 1980s, as reported in the August issue of American Journal of Preventive Medicine .
But Mark Blaxill of Minds Safe argues that the Danish study is "misleading and distorted." He noted that in 1995, the Danish health registry began tracking a new category of patients, outpatient called autism. This and other factors, he says, are artifacts that confuse interpretation. Madsen replied that unpublished analysis without external consultation has shown the same upward trend.
epidemiologist Craig Newschaffer of Johns Hopkins University in Baltimore said that these ecological studies have inherent limitations, because they look at people rather than studying individual exposure. Although current studies are not likely to end the controversy in the United States, where many lawsuits have been filed, the new results are reassuring to the World Health Organization, which continues to recommend the use of small amounts of thimerosal to limit the costs of essential vaccines.
Related Sites
FDA information on thimerosal
the WHO policy on thimerosal
Minds Safe
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