THIMEROSAL AND AUTISM

Are childhood vaccines one of the most powerful preventative health measures ever introduced; or will they in time be shown to have contributed to serious chronic illness? Depending on who you ask, vaccination is either a blessing or a potential curse in the lives of our infants and children. While controversy and debate over many aspects of vaccination continues to rage, one of the fiercest controversies relates to a potential link between childhood vaccinations and an explosive increase in the incidence of autism.

Autism is a spectrum of disorders ranging in severity from bizarre violent behaviour to difficulty with communication and social interaction, along with repetitive behaviours. Autism usually appears before a child is three. The western world is witnessing an alarming increase in the diagnosis of autism. In America, between 1992 and 1998 there was an increase of autism diagnsoses of nearly 180%. In California the increase in the past decade has been a whopping 273%. There has been a similarly alarming increase in autism numbers in other western countries.(am trying to find NZ stats!!)

Why are autism numbers increasing? Many parents, researchers, scientists and doctors are questioning a possible connection between an increase in childhood vaccines and the autism epidemic. The American National Vaccine Information Centre reports that "parents are reporting to our organisation in record numbers that their children are becoming autistic after vaccination. Our experience in the past seventeen years has been that, as immunizations rates have increased significantly in all states, we have seen an increase in reports of vaccine reactions, including immune system dysfunction and autistic behaviours".

The autism/vaccine debate is two pronged. Firstly there is the question of a possible link between the triple vaccine MMR and autism (a debate not explored in this article). While there are a number of alarming studies, authorities strongly refute any such connection. Then there is the question of whether the use of a common mercury based vaccine preservative thimerosal is linked with the autism epidemic. Introduced as a preservative in 1930, Thimerosal went into common use without review by the FDA because it was "assumed" to be safe! Mercury is a known neurotoxin with neurological effects at exceedingly low doses of exposure, especially toxic to infant brains which are still developing. Besides vaccination, the most common environmental mercury exposure now comes in the form of eating fish, and having amalgam dental fillings. While the thimerosal/autism debate remains controversial, medical and governmental authorities are increasingly examining the connection. Says Boyd Haley, chemistry professor at the University of Kentucky "thimerosal is extremely toxic. The preliminary data is convincing and does indicate that vaccines are the most likely suspect for causing autism."

In 2000 a scientist from the US Centers for Disease Control and Prevention gave a presentation based on a database of 400,000 children with evidence of harm from vaccination. Dr Verstraeten concluded that the screening analysis suggested "statistically significant associations" between neurological disorders such as ADD and speech and language disorders, and exposure to mercury from thimerosal containing vaccines before the age of six months. In 2004 a panel used the same data to study the possible link between thimerosal and autism. They concluded that children who were given three thimerosal containing vaccines were 27 times more likely to develop autism than children who receive thimerosal free vaccines. The American Autism Research Institute (ARI) claims its database contains thousands of cases of previously healthy children who began exhibiting autistic behaviours shortly after receiving routine childhood vaccines.

Obviously not all children who receive the regular schedule of childhood vaccines develop autism. It is theorised that some children have a genetic predisposition to mercury sensitivity, which combined with the mercury injected into their body during vaccination, results in neurological damage and autism. A 2001 study from the Chicago based Pfeiffer Centre involving 503 autistic children showed that in 99% of autistic children a family of proteins essential for disposing of mercury and other heavy metals is missing or disabled.

After years of assuring concerned parents that thimerosal was safe, vaccine manufacturers have now removed it from most childhood vaccines. The New Zealand schedule still includes a thimerosal containing tetanus booster shots given at 11 years of age; until this year the flu vaccine has also contained thimerosal, and there is no guarantee that next years flu vaccine will not once again contain the preservative. Thimerosal is still used in a range of New Zealand vaccines administered to adults.

Safe exposure to mercury is thought to be around 0.1mcg per kilogram per day. Considering that a hepatitis B injection used to contain 12mcg; DTP and Hib routinely administered on the same day contained 50mcg of mercury (60 times safe level); and Hep B and polio administered on the same day contained 62.5mcg (78 times safe level), the potential for thimerosal to cause toxicity problems does not seem beyond the realms of possibility.

Controversy continues with many authorities strongly refuting any possibility of a connection between thimerosal and autism. The American Institute of Medicine of the National Academies revisited the question of thimerosal and autism recently in light of several recent studies exploring the link. Five large epidemiological studies conducted since 2001 each failed to demonstrate a link between thimerosal and autism. The committee also reviewed 5 studies that did demonstrate such a link, and discredited each of the studies based on experimental design or methods of statistical analysis.

While experts continue to argue the thimerosal/autism connection, most parents are happy to know that their children are no longer receiving a dose of mercury along with their vaccination!

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