'Potent Neurotoxin' Thimerosal Is Still Used in Some Flu Vaccines, Scientist Says

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More than two decades ago, a little-known mercury-based product, thimerosal, was approved by the Food and Drug Administration to be used as a vaccine preservative. Since then, many parents and scientific studies have questioned whether it is responsible for the current epidemic of neurological and developmental disorders, such as learning disabilities and autism.

In July 1999, U.S. health agencies and the American Academy of Pediatrics (pdf) reduced or eliminated thimerosal from vaccines as a “precautionary measure.”

Yet up to 25 micrograms of thimerosal remain in several versions of the influenza vaccines recommended this flu season, including those administered to pregnant women, infants, and children, and it is still present in some multi-dose vial vaccines, despite hundreds of studies showing thimerosal is harmful.

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“The CDC created the illusion that they were removing thimerosal from vaccines between 2001 and 2003 through the voluntary phase-out of its use as a preservative in the HepB, HiB, and DTaP vaccines. However, it was reintroduced into the prenatal/infant/child vaccination schedule via the flu shot at the same time,” Brian Hooker, chief scientific officer at Children's Health Defense, who holds a doctorate in biochemical engineering, told The Epoch Times in an email.

“In 2004, the CDC indicated that the mercury-containing flu shot could be given during any trimester of pregnancy, meaning that the developing embryo/fetus could be exposed to 25 micrograms of mercury," he said.

What is Thimerosal?

Thimerosal is an organic mercury compound used since the 1930s as a vaccine preservative. It is approximately 50 percent mercury by weight and produces ethylmercury as a metabolite. This metabolite then changes to inorganic mercury in the body and accumulates primarily in the brain and kidneys.

According to the Environmental Protection Agency (EPA), mercury is a naturally occurring chemical element found in rock in the earth's crust. In its various forms, mercury is highly toxic, and exposure can harm the brain, heart, kidneys, lungs, and immune system. Yet thimerosal present in vaccines is considered safe, according to U.S. health agencies.

When it comes to different forms of mercury, organic mercury is more toxic than inorganic mercury—which is mercury combined with other elements.

Thimerosal Toxicity

Mercury and mercuric compounds like methylmercury, ethylmercury, and thimerosal have long been considered nephro- and neurotoxicants.

Mercury is "a potent neurotoxin and will destroy neurons (via demyelination) on contact," Mr. Hooker said.

Methylmercury—exposure of which occurs mainly through the consumption of fish or inhalation of mercury vapors—is regarded as one of the most toxic non-radioactive substances known to man. Although methylmercury has received more attention, studies have shown that the effects of ethylmercury toxicity are comparable to methylmercury toxicity. Methylmercury and ethylmercury are the most prevalent forms of exposure for fetuses, newborns, young children, and pregnant and breastfeeding mothers (pdf).

Before thimerosal was removed from most vaccines, over 30 U.S.-licensed vaccines contained thimerosal as a preservative. It was estimated that children may have received 200 mcg of ethylmercury from vaccines during their first six months of life—a value that far exceeded the EPA’s recommendations.

Although the CDC states that the "body eliminates thimerosal easily," that it "does not stay in the body for a long time,” and the medicinal use of products containing thimerosal has a record of being “very safe,” this contradicts more than 75 years of research from independent scientists who have consistently found thimerosal to be harmful.

“Mercury is the second most toxic naturally occurring element on the planet. It is preposterous to include it as an additive in any vaccine.” said Mr. Hooker.

According to a paper published by the Immunization Safety Review Committee established by the U.S. Institute of Medicine, thimerosal—a thiosalicylate salt of ethylmercury—once administered, quickly disassociates from thiosalicylic acid and binds to blood and other tissues.

According to neuropharmacologist and thimerosal expert Richard Deth, the toxic effects of organic forms of mercury can remain in tissues for many years, especially in the brain, due to the retention of released inorganic mercury—which occurs at a greater rate for ethylmercury than for methylmercury (pdf). Mr. Deth says the belief that thimerosal is safe based on lack of entry into the brain is “patently false” (pdf).

A study by Thomas Burbacher et al. was noted in which thimerosal was administered intramuscularly to infant monkeys at weekly intervals as a vaccine at a level comparable to what human infants receive during vaccination. Researchers assessed mercury levels in the blood and brain and compared levels to orally administered methylmercury. Although researchers found thimerosal-derived ethylmercury was cleared more readily from blood and was present in lower amounts compared to methylmercury in the brain, they observed significant entry into the brain and found that a greater proportion remained in the brain long term compared with methylmercury.

“Accordingly, at equal doses, thimerosal carries a higher risk of producing neurological impairments than methylmercury,” Mr. Deth said.

Link to Neurodevelopment Disorders

Decades ago, U.S. health agencies acknowledged that it was biologically plausible thimerosal exposure through childhood vaccinations could cause neurodevelopmental disorders and harm the kidneys. Still, there had been no published, controlled epidemiological studies on thimerosal-containing vaccines and neurological disorders.

The CDC states on its website that “data from many studies show no evidence of harm caused by the low doses of thimerosal in vaccines,” yet hundreds of studies, including CDC studies, show the opposite. In one study, CDC epidemiologists (pdf) analyzed data from the Vaccine Safety Datalink and found a 7.6 times increased risk of autism from exposure to thimerosal during infancy.

According to a 2014 paper in BioMed Research International, the CDC’s stance that thimerosal is safe and does not cause or contribute to autism is based on six studies coauthored or sponsored by the CDC in the late 1990s.

“Conceivably, if serious neurological disorders are found to be related to thimerosal in vaccines, such findings could possibly be viewed as damaging to the vaccine program,” researchers wrote.

Parents of 5,600 families of children diagnosed with autism had previously filed claims with the National Vaccine Injury Compensation Program alleging their children developed autism after receiving thimerosal-containing vaccines. The Omnibus Autism Proceedings, held from 2007 to 2008, examined these claims.

Studies examining the effects of thimerosal on infants and children show thimerosal may cause death, acrodynia, poisoning, allergic reaction, malformations, autoimmune problems, Well’s syndrome, developmental delay, and neurodevelopmental disorders, including autism.

A 2004 comparative study using CDC data to evaluate the effects of the MMR vaccine and mercury from thimerosal-containing childhood vaccines on the prevalence of autism found a “statistically significant odds ratio” for the development of autism following increasing doses of mercury from thimerosal-containing vaccines. Researchers said their results aligned with other studies showing a “biological plausibility and epidemiological evidence” of a direct relationship between increasing doses of mercury from thimerosal-containing vaccines and neurodevelopmental disorders.

A study published in Pediatric Rehabilitation using CDC data from the Vaccine Adverse Event Reporting System (VAERS) and the U.S. Department of Education evaluated whether mercury from thimerosal in childhood vaccines contributed to neurodevelopmental disorders. Results showed an increase in neurodevelopmental disorders from both data sets “closely linearly correlated with increasing doses of mercury from thimerosal-containing childhood vaccines.”

A 2003 study published in the International Journal of Toxicology compared children who received diphtheria-tetanus-acellular pertussis (DTaP) thimerosal-containing vaccine to a group of children who received a thimerosal-free version of the vaccine administered from 1997 through 2000 and assessed adverse events reported to VAERS. Results showed children who received the thimerosal version of the vaccine experienced “significantly increased odds ratios” for autism, mental retardation, speech disorder, personality disorders, and thinking abnormalities.

These results coincided with previously published epidemiological evidence showing an association between thimerosal-containing childhood vaccines and neurodevelopmental disorders and a two- to sixfold statistically significantly increased reporting rate of neurodevelopmental disorders to VAERS following thimerosal-containing DTaP vaccines, according to the study.

A 2006 ecological study found significant reductions in the proportion of neurodevelopmental disorders reported to VAERS as thimerosal was removed from childhood vaccines in the United States from mid-1999 onward.

Aside from research on thimerosal’s potential link to neurodevelopmental disorders, U.S. health agencies have not adequately studied how thimerosal interacts with other heavy metals in vaccines, such as aluminum—a neurotoxin associated with its own adverse effects—nor has the agency studied the cumulative effects of administering multiple vaccine doses containing these ingredients in children.

The Epoch Times reached out to the CDC for comment.