I finally explored the debate over childhood vaccines and autism. Thimerosal is a preservative used in vaccines to inhibit bacterial and fungal growth containing 49.6% Mercury. It has been used since the 1930s. In 1947 the first cases of Autism were noted. Reporting and Diagnosis of Autism has grown, especially in the 1990s. Today up to 1% of children have some signs and symptoms of Autism Spectrum Disorder.
The symptoms of Autism range from difficulties in verbal communication, a need for routines, and limited interest in play and relationships. The signs and symptoms of Autism were noted in the 1990s to appear around the same time as childhood vaccinations. Coincidence or Not? Other neurodevelopmental disorders have also been linked to Autism, such as ADHD and language/speech delay.
With the growing debate the FDA in 2001 required that Thimerosal be eliminated or only used in trace amounts in vaccines for children under the age of 6. Today Thimerosal has been eliminated from most vaccinations except it still exists in a concentration of 0.01% in: influenza, Diphtheria & Tetanus, Tetnus booster, and some Meningococcal Vaccines. In my research I tried to study the effects of Thimerosal on children since these changes were put in place.
I have discovered why this debate still exists. Most research in animal models is done with methylmercury. However, Thimerosal is degraded to ethylmercury which is chemically different from methylmercury - but yes still a type of mercury. Some argue that you can study methylmercury and apply the results to ethylmercury in Thimerosal. Others argue that the type of mercury in Thimerosal is eliminated faster and to a fuller extent compared to other forms of mercury. However, the question still exists: What does the small percentage of ethylmercury that remains in the body do to children? Hence, this debate is still not resolved. The research I found had arguments on both sides that were reputable and convincing. I'll try to present both sides of the debate below.
Some of the evidence that links Thimerosal to neurodevelopmental disorders:
-2007 New England Journal of Medicine: Association with Mercury exposure and detrimental behavior regulation, motor tics and phonic tics . Increased exposure to mercury during the neonatal period was related to poor speech articulation.
-2001 Molecular Psychiatry Journal: Clinicians noted elevated mercury levels in the urine of autistic patients. After chelation of mercury there was an improvement in Autism symptoms. Vaccines were the only mercury exposure in this study.
- 2003 CDC: 2003: CDC Analysis of HMO data showed increased mercury exposure was associated with language delay.
- Thimerosal in Rats caused increased activity of endogenous opioids. Autism is associated with the dysregulation of endogenous opioids.
Some of the evidence that finds no link between Thimerosal and neurodevelopmental disorders:
- Ethylmercury (Thimerosal) and methylmercury are chemically different.
- JAMA: Ethylmercury has a shorter half life than methylmercury and is eliminated rapidly in stools.
- Recent studies in animal models suggest that methylmercury may not be suitable to assess the risk of exposure to thimerosal.
- Permissible doses for ingestion of methylmercury by the Environmental Protection Agency is 0.1µg/kg per day.
Average 6 month year old: 7.5kg
Average Permissible dose: 0.75µg/day
Average Permissible dose in 6 months: 140µg
The maximum exposure from vaccines in the first 6 months of life is less than 3 micrograms of mercury.
- 2003 JAMA article: Risk of autism did not differ significantly between children vaccinated with thimerosal vaccines and non-thimerosal vaccines.
- 2004 The IOM Immunization Safety Review Committee: Considered new evidence and still concluded that there is NOT a causal relationship between Thimerosal and Autism.
- 2004 American Academy of Pediatrics: Data from Denmark and Sweden was evaluated.
Exposure to thimerosal in vaccines was eliminated in 1992 in these countries BUT autism rates continued to increase!
Again, I tried to focus on the current situation and studies since the new regulations in 2001. The conclusion from all these studies: There is evidence on both sides that is reputable. However, enough research has still not been done. This may always be the case because it would be unethical to sign a child up for such studies. Vaccines help prevent disease, very serious scary diseases and it is important to get your child vaccinated. Would I get my child vaccinated? yes. Would I pay more for Thimerosal FREE vaccines if available? yes. Thimerosal is still mercury and it's effects on children are not clear BUT the benefits of vaccinations have been proven.
