In my last article about vaccines and the fraudulent accusation that they are associated with or cause autism, I outlined how the concern for the health effects vaccinations began with an observation that the number of cases of autism worldwide appeared to almost double in the 1990s. Again, it still is debated as to what “caused” this spike, but we suspect it was a change in the diagnostic definitions of autism, increased awareness of autism and other mental health disorders in children, and/or an increase in screening for autism.
Understandably, worried parents at the time began to search for what could be the “cause” of this perceived increase in autism. After the vaccine itself was targeted as a potential cause, the scientific community raced to “debunk” this, and I believe we did so quite successfully.
Despite this evidence, some people have now turned to blame the culprit on the preservative thimerosal in vaccines. I’m here today to give you the evidence about the preservative thimerosal specifically and how it is not associated with autism.
There is an organization called the Vaccine Adverse Event Reporting System (VAERS). Taken from their website, VAERS is “a national vaccine safety surveillance program co-sponsored by the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC). The purpose of VAERS is to detect possible signals of adverse events associated with vaccines… Reports are welcome from all concerned individuals: patients, parents, health care providers, pharmacists and vaccine manufacturers.”
VAERS relies on people to voluntarily report possible vaccine adverse events. To make a study from this pool of data would be inherently biased. Unsurprisingly, there were studies done with data taken directly from VAERS that suggested an associated between thimerosal and autism. These studies suggested that the rate of autism was higher in children who have received thimerosal-containing vaccinations compared to those who did not. These studies are flawed and biased based on the way data was collected.
Long story short, there have be dozens of very large and well-designed studies and systematic reviews that show no evidence between thimerosal-containing vaccines and autism. One specific study (A 2014 systematic review that included 718,200 children and one case-control study including 1008 children) found absolutely no relationship between the preservative thimerosal exposure (including mercury or ethylmercury exposure) and Autism.
Some parents and reporters have suggested that autism is an expression of mercury poisoning. This is largely related to their subjective opinion that mercury toxicity has similar symptoms and clinical signs as autism.
Some of the physical signs and symptoms of mercury poisoning include: severe difficulty walking, narrowing of the vision, difficulty articulating words or slurring speech, changes in sensation or weakness in the limbs, and sometimes with chronic exposure to mercury they can have a small head. These are VERY clinically different than the signs of Autism Spectrum Disorder which include: repetitive behaviours, delayed speech, hypersensitivity to sounds or other sensory stimuli and possibly decreased sensitivity to pain, rigid behaviours or need for adherence to routine and sameness, absence of a social smile, difficulty interacting socially with peers and limited eye contact, and sometimes they can have a larger than normal head.
Autopsy reports of children with autism compared to children with mercury poisoning show very different changes in the brain. To date, there has been no evidence suggesting a causal relationship between thimerosal and autism. Furthermore, the changes seen with mercury exposure and poisoning are vastly different than the changes seen in brains of children with autism.
With the concern of “mercury poisoning” in mind, some parents went to far as the get chelation therapy for their children. Chelation therapy is a chemical that is inserted (usually by IV into the blood) into the body with the intent of binding to heavy metals, and removing them from the body. The intent of the chelation therapy here was to remove the heavy metal mercury from a child’s body. These parents then rushed to the internet with subjective reports that their child was “cured” from autism.
Studies that measure the mercury levels in hair, urine, or blood of children with autism show no difference in mercury levels compared to children without autism. There is no evidence that chelation therapy to remove mercury improves or cures autism.
The exposure to low-dose thimerosal that is present in vaccines has no demonstrated effects on the nervous system. Interestingly, the incidence of autism has continued to increase even after the use of thimerosal in vaccinations has been discontinued. Finally, The World Health Organization Global Advisory Committee on Vaccine Safety has concluded that the available evidence strongly supports the safety of thimerosal as a preservative for inactivated vaccines and that no additional studies are necessary to confirm this.
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1. Centers for Disease Control and Prevention (CDC). Summary of the joint statement on thimerosal in vaccines. American Academy of Family Physicians, American Academy of Pediatrics, Advisory Committee on Immunization Practices, Public Health Service. MMWR Morb Mortal Wkly Rep 2000; 49:622, 631.
2. Miles JH, Takahashi TN. Lack of association between Rh status, Rh immune globulin in pregnancy and autism. Am J Med Genet A 2007; 143A:1397.
3. Joint statement of the American Academy of Pediatrics (AAP) and the United States Public Health Service (USPHS). Pediatrics 1999; 104:568.
4. Thimerosal in vaccines–An interim report to clinicians. American Academy of Pediatrics. Committee on Infectious Diseases and Committee on Environmental Health. Pediatrics 1999; 104:570.5.
5. Redwood L, Bernard S, Brown D. Predicted mercury concentrations in hair from infant immunizations: cause for concern. Neurotoxicology 2001; 22:691.