Vaccinations and Autism

From LoveToKnow Autism

Among the most controversial issues surrounding the rise in autism spectrum disorders is the relationship between childhood vaccinations and autism. While experts on one side of the debate are convinced that there are various links between the administration of vaccines and the onset of autism, the CDC disagrees, stating that here is no indication of a cause and effect relationship. Each side of the debate can quote conflicting scientific studies supporting their point of view, adding further controversy to this already heated dispute.

Autism vaccination rulings

The Case for a Vaccinations and Autism Connection

Many autism experts, physicians, and members of the autism community are convinced that vaccines trigger the onset of autism symptoms. While many among this group cite different theories of why this happens, the point of agreement among them is that some or all of the vaccines routinely given during childhood are the cause of much of today's ever increasing autism cases.

Mercury

One prominent theory involves a preservative called thimerosal that was once a standard ingredient in many childhood vaccines and is still present in many vaccine preparations. Thimerosal contains 46.9 percent ethyl mercury. Mercury is a known neurotoxin, a dangerous metal second only to uranium among the most harmful natural substances. Since autism spectrum disorders are neurological disorders, many believe that the injection of thimerosal into the bodies of children is at the root of many autism cases.

One viewpoint on the possible thimerosal-autism connection concludes that some children's systems are less efficient at cleansing heavy metals like mercury out of the body, explaining the fact that mercury poisoning does not occur in all vaccinated children. Many cite a correlation between the increase in autism cases and the gradual increase in thimerosal exposure as the number of mandatory childhood vaccinations have increased from ten during the 1980s to the thirty that are required today. The symptoms of mercury poisoning and autism are strikingly similar, as illustrated by a comparison chart found at the bottom of the National Autism Society's page on thimerosal.

Among the scientific studies that lend support to a possible connection between mercury content in vaccinations and autism is one published in the Journal of Child Neurology, Vol. 22, No. 11, 1308-1311 (2007). Done by M. Catherine DeSoto, PhD and Robert T. Hitlan, PhD, both of the Department of Psychology, University of Northern Iowa, this study finds that a different prominent study that showed no link between mercury and autism used a flawed data set to reach that conclusion. Upon reanalyzing corrected data, results of this study state that a significant relationship does exist between autism diagnosis and blood levels of mercury. The authors of the study say that hair-sample analysis results support the theory that individuals with autism may be less efficient at eliminating mercury from the blood.

Another 2008 study published in the Journal of the Neurological Sciences supports a connection between vaccines containing mercury and autism. This study assessed computerized medical records in the Vaccine Safety Datalink to conclude that rates of autism spectrum disorders and other neurological problems rose consistently with increased exposure to thimerosal in vaccines.

MMR Vaccine

Another theory on the possible connection between autism and childhood vaccinations involves the MMR vaccine. A number of studies support this theory as well, including one conducted in Denmark by G.S. Goldman, Ph.D. and F.E. Yazbak, M.D., F.A.A.P. The authors of this study examined data collected on the rates of MMR vaccination after they became mandatory in 1987 and the rate of autism diagnosis, concluding that there was a correlation between the introduction of MMR and autism spectrum disorders. Regressive autism is the form of this disorder that many suspect as being linked to the MMR vaccine, as its onset often occurs after the vaccine has been given. Regressive autism is an autism spectrum disorder in which children develop according to typical expectations for several years, then begin to lose ground, regressing until they display the telltale symptoms of autism.

The Case Against a Connection

The medical establishment has long denied any correlation between autism spectrum disorders and vaccinations, a viewpoint that is seconded by government health officials. Those on the no connection side of the debate have a variety of studies to support their opinion on the matter as well. Among these studies is a review done by the Institute of Medicine, which revisited published and unpublished studies on possible biological factors that could indicate that vaccinations may cause autism. From this review, the committee concluded that the evidence of these studies overwhelmingly favors the position that there is no connection between either thimerosal containing vaccines or the MMR injection. Another study supporting the views of the medical community is a case-controlled study published by the Public Library of Science in September 2008. The stated goal of authors of this study was to determine whether autism and GI inflammation could be connected with the administration of the MMR vaccine. Tissue samples were taken and studied from 25 children with autism and 13 with GI symptoms alone. The results state that no differences were found between the case group and the control, providing strong evidence against a cause and effect relationship between MMR exposure and autism or GI tract disturbances.

According to the CDC, any correlation between the administration of the MMR vaccine and regressive autism is coincidental, rather than a cause and effect relationship. A number of studies support this conclusion. Among the latest of these is one funded by the CDC and the National Institute of Health, published on September 4, 2008, stating that the results provide strong evidence against any association between MMR exposure and autism. As for vaccines with thimerosal, the official position of the CDC is that there is no connection between vaccines and the rising incidence of autism. In support of this stance are many studies, among them one titled Safety of Thimerosal-Containing Vaccines: A Two-Phased Study of Computerized Health Maintenance Organization Databases, which states in its conclusions that while there were some conflicting findings, no significant consistent connection was found between thimerosal in vaccines and autism spectrum disorders.

More Must Be Done

The debate about vaccinations and autism is not likely to be resolved based on the evidence available today. Many of the studies, no matter which side of the debate their conclusions support, are not definitive. Many of the researchers involved in these projects agree on one crucial point, there is a need for more research to determine whether vaccines are connected to the rapid rise in autism spectrum disorders.

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