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Autism-Vaccine Link: Does It Really Exist?

Written by Neil Simmons

Tuesday, 12 June 2007

Autism is a complex developmental disorder that severely impairs a child's ability to communicate and interact with other people. Although the precise cause of autism is unclear, a plethora of theories have been suggested. One theory suggests a genetic link, while another holds vaccines containing mercury as the culprit. Parents of autistic children are now seeking legal recourse on whether mercury in vaccines caused autism in their children.

Thimerosal is a preservative in vaccines that contains 49 percent ethyl mercury. Mercury is a known neurotoxin or in other words is a chemical that causes untold harm to the brain, especially a child's developing brain. Scientists thought that autism might be one such toxic manifestation of mercury in vaccines. In 2002, thimerosal was phased out of childhood immunizations mainly because the Public Health Service and the American Academy of Pediatrics advocated it.

However it is possible that the mercury in the vaccines administered to children before 2002 did play a role in the development of autism. In the present case Cedillo v. Secretary of Health and Human Services, the United States Court of Federal Claims in Washington is all set to hear data that vaccines containing mercury are a causal factor in autism.

The case will be followed very keenly because there are another 4,800 such cases pending before the court.

Autism-vaccine links emerged in the late 1990s when the State of California released a report suggesting a 273 percent increase in the number of persons with autism between 1987 and 1998, the New York Times reports.  The cases of autism are definitely on the rise in American children, whether it is due to improved diagnosis or due to other factors remains unclear.

In 2004, the Institute of Medicine examined data on links between vaccines containing mercury and the incidence of autism and found no evidence linking thimerosal to autism. The Institute of Medicine's panel based its conclusions on five large studies conducted in United States, Denmark, Sweden and Britain in 2001. These studies examined thousands of children, but failed to find any link between autism and thimerosal.

The IOM report said it was an undisputed fact that high doses of mercury did cause substantial neurological damage. However no symptoms resembled that of autism, the report suggested. It added that genetics was the main causative factor as many studies had noted that autism started prenatally.

A review by the Environmental Working Group suggested that autistic children had a biomarker that rendered them susceptible to mercury and heightened their risk of developing the neurological disorder.  The report cited a study by Dr. Jill James of the University of Arkansas School of Medicine, which found that children with regressive autism had high levels of oxidative stress, which made it hard for their bodies to get rid of mercury.

The study cited the following factors as well (as available on
* The indisputable toxicity of mercury to the brain, particularly the developing brain (Limke 2004, Clarkson 2002, Mahaffey 1999).
* Peer-reviewed reports showing that autistic children are extremely poor at ridding their bodies of mercury as measured by mercury hair levels (Holmes 2003).
* The recent finding that autism-like symptoms are triggered by thimerosal in mice with a predisposition to autoimmunity (Hornig 2004).
* The fact that the prevalence of autism in boys is four times that in girls, and that boys have elevated incidence of damage from mercury exposure in epidemiologic studies (Vahter 2002).

The study said that it did not find a credible link between mercury in vaccines and autism, but there was sufficient evident to suggest mercury played some role.

This theory was reinforced by a study in 2006 which showed that autism cases declined when mercury was banned from vaccines. Using data from CDC’s Vaccine Adverse Event Reporting System (VAERS) and the California Department of Developmental Services (CDDS), lead authors David A. Geier, B.A. and Mark R. Geier, M.D., Ph.D found that autism rates hit a high of 800 in May 2003, but dropped to 620 in 2006.

The authors suggested that the 22 percent decline in autism cases was mainly due to the restriction of mercury in vaccines.

The U.S. Centers for Disease Control and Prevention estimates that one in every 150 children has autism and that 560,000 people aged till 21 in the United States have autism.

Experts have tried to dispute the vaccine-autism link by suggesting that children are naturally distressed by shots and that this is the age when autism is first diagnosed leading parents to believe that the vaccines cause it.

It will be interesting to see what the U.S. Court of Federal Claims rules in the autism-vaccine case pending before it. This ruling might set off a legal time-bomb if it decides that mercury in vaccines is indeed responsible for autism. However a battery of scientists is also ready to give the flip side of the opinion.

The case is expected to last for three weeks.

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