The controversy over thimerosal: Unraveling the link between vaccines and neurodevelopmental disorders
By oliviacook // 2025-03-08
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  • Thimerosal, a mercury-based preservative, was commonly used in childhood vaccines like DTP and Hib from the 1990s, raising safety concerns.
  • Exposure to thimerosal through vaccines exceeded federal safety guidelines, potentially causing neurological damage due to mercury's neurotoxicity.
  • A study linked thimerosal to neurodevelopmental disorders, including autism, infantile spasms and mental retardation.
  • The rise in neurodevelopmental disorders, including autism, coincided with the use of thimerosal in vaccines.
  • Despite conflicting research and the Institute of Medicine's 2004 conclusion, thimerosal's safety remains a concern, and further studies are needed.
For decades, vaccines have played a crucial role in preventing deadly diseases, saving millions of lives worldwide. In the 1990s, a heated debate began to simmer in the medical community and among parents in the United States. At the heart of the controversy was a substance called thimerosal, a mercury-based preservative historically used in many childhood vaccines. This debate has raised critical questions about the safety of vaccines and their potential impact on children's neurodevelopment and brain health – fueling scientific inquiry and public concern.

What is thimerosal and why was it used?

Thimerosal is a compound containing ethylmercury, a form of mercury. It was commonly added to vaccines to prevent contamination by bacteria and fungi. During the 1990s, children in the U.S. received multiple vaccines containing thimerosal, including the DTP (dipththeria-tetanus-pertusis) and Hib (haemophilia influenza type B) vaccines. These vaccines were administered at two, four, six, 15 to 18 months of age and four to six years (before school entry) – leading to cumulative mercury exposure. (Related: Studies suggest link between childhood vaccinations and rise in autism prevalence.) Concerns arose because the amount of mercury the children were exposed to through these vaccines exceeded federal safety guidelines for mercury ingestion. For instance, if a child received all recommended vaccines with thimerosal during the first 18 months of life, they could be exposed to as much as 237.5 micrograms of mercury. This is significant because mercury is a known neurotoxin and excessive exposure can lead to neurological damage.

Comparing vaccines and their effects

A study published in the Journal of Toxicology and Environmental Health, Part A aimed to investigate whether there was a link between thimerosal-containing vaccines and neurodevelopmental disorders. The researchers compared children who received the DTP vaccine, which contained thimerosal, with those who received the DTPH (Diphtheria-Tenatus-Pertusis-Haemophilus B) conjugate vaccine, which is a combined vaccine with less thimerosal. The study analyzed data from the Vaccine Adverse Event Reporting System (VAERS), a database maintained by the Centers for Disease Control and Prevention (CDC). The study found a significant association between thimerosal-containing vaccines and several neurodevelopment disorders, including autism, cognitive impairment, mental retardation, infantile spasms, speech and language delays and abnormal motor and thinking patterns. Children who received the DTP vaccine (with higher thimerosal content) were more likely to have these disorders compared to those who received the DTPH vaccine (with lower thimerosal content). The study controlled for various factors to minimize bias and the results suggested that the increased risk was not due to chance. During the same period that thimerosal was widely used in vaccines, there was a noticeable rise in the prevalence of neurodevelopmental disorders in the United States. For example, autism, once considered "rare," is now estimated to affect one in 166 children. This dramatic increase has led some researchers to question whether environmental factors, such as mercury exposure, could be playing a role.

The science behind mercury's effects on the brain

Beyond epidemiological data, laboratory research has explored the biological effects of thimerosal on the nervous system.  Some key findings include:
  • Reduced ability to eliminate mercury. Studies suggest that autistic children may have impairments in detoxifying mercury, leading to higher internal mercury levels compared to neurotypical children.
  • Impact on brain cells. Laboratory studies show that even low concentrations of thimerosal can disrupt nerve cell growth, damage DNA and trigger cell death.
  • Animal studies. In one study, mice given thimerosal at doses mimicking childhood vaccine schedules developed autism-like symptoms, including social withdrawal and abnormal brain structure.
  • Increased sensitivity in males. Research indicates that males may be more vulnerable to mercury toxicity, which aligns with the higher prevalence of autism in boys compared to girls.

Conflicting views and ongoing research

The findings of this study contrast with the 2004 conclusion of the Institute of Medicine (IOM) that there is no link between thimerosal and autism. However, the IOM's 2005 report raised concerns about the CDC's handling of vaccine safety data, suggesting that the issue is far from settled. While thimerosal has been largely removed from most childhood vaccines in the U.S. since 2001, it is still used in some vaccines, such as certain flu shots. Moreover, many countries worldwide continue to use thimerosal in pediatric vaccines. The World Health Organization (WHO) and some vaccine manufacturers argue that the benefits of thimerosal in preventing vaccine contamination outweigh the potential risks. The association between thimerosal and neurodevelopmental disorders is a contentious issue that requires further investigation. While the debate continues, it is essential to prioritize the health and safety of children.  Continued vigilance in evaluating vaccine ingredients is essential to ensure safety for all children. Scientific inquiry should remain open, and further studies should be encouraged to clarify any remaining uncertainties. Listen to Dr. Mary Megson speak on autism epidemic and vaccines in this clip. This video is from the OneNinetyFiveNationsRising channel on Brighteon.com.

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Autism begins during pregnancy, may be caused by mercury in dental amalgam and thimerosal in flu shots, warns science paper. The corrupt medical establishment and the vaccine industry doesn't want you to see these studies, which link VACCINES to AUTISM. The mercury-autism connection: What the science says. Sources include: MSDManuals.com KidsHealth.org ResearchGate.net TAndFOnline.com Business-Standard.com Brighteon.com
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