The Vaccine-Autism Link: Facts and Myths

Autism researchers say there is no link between thimerosal and the disorder.

ByABC News
February 9, 2009, 9:13 PM

June 11, 2007 — -- A federal court begins hearings today on the more than 4,800 claims by parents of autistic children that the mercury-containing preservative thimerosal, present in certain routine vaccinations, led to their children's disorders.

It is the day that many of these families have pushed for since 1999.

Concerns about thimerosal's possible link to autism have gained publicity in recent years as the occurrence of autism in children has climbed steadily in the United States. Doctors have struggled to find a clinical reason for the increase. Because vaccinations are mandatory for all children at a certain age, some parents and doctors believe the vaccines indicate a common link that cannot be ignored.

However, current research weighs heavily against the premise of a thimerosal-autism link, as thus far a number of large scientific studies have shown no association between the two.

Most recently, a review of past research published this month in the journal Current Opinion in Infectious Diseases suggests "increasingly convincing epidemiologic and laboratory evidence against a causal relation of several alleged adverse events following immunization."

The findings bolster the position that has been steadfastly held by the Institute of Medicine (IOM) that no link can be established between thimerosal and autism.

Prior to the summary, most physicians and researchers have agreed that the suggestion of such a link is likely baseless, as seen in their previous statements on the issue (responses collected from telephone interviews conducted in June 2005):

The issue may be a moot point. Despite the lack of scientific evidence of a link between thimerosal and autism, a number of public health organizations and vaccine manufacturers agreed in July to reduce or eliminate thimerosal from vaccines as a precautionary measure. As a result, none of the vaccines used in the United States to protect preschool children against 12 infectious diseases contain thimerosal as a preservative (with the exception of some influenza vaccines), according to the CDC.

Some researchers say that the absence of a link has already been demonstrated in a real-world setting in Denmark, where thimerosal was removed from all vaccines in 1992. Despite this move, autism rates in the country continued to rise until 2004, the year in which the Danish study was terminated.

But some said the suggestion that vaccines could be to blame for autism may already be having an impact on public health, as parents concerned about the possibility of dangers may be less inclined to have their children immunized:

"Especially in the U.K. and Ireland, home to the early proponents of a connection between MMR and autism, decreased immunization rates have resulted in needless epidemics of measles which have killed several children."

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