Should We Still Be Concerned about Thimerosal?

Approximately fifteen years ago, Dr. Mark Geier and his son David conducted research that demonstrated that Thimerosal, a dangerous organomercury compound used as a preservative in vaccines, can increase a child’s risk for developing neurological disorders like autism. Why did those like Geier believe Thimerosal poses a potential threat to children? Research had shown that for months after thimerosal exposure, this compound can alter the quantity of neurons found in the hippocampus and thalamus, parts of the brain that play a crucial role in cognitive development.

In response to these groundbreaking findings and the public awareness that ensued, the CDC decided to eliminate the presence of Thimerosal in many common childhood vaccines. For many, this was enough to subdue fears and more or less wipe the issue from public consciousness. However, for those like Dr. Mark Geier, Thimerosal was still very much an issue of concern, as this preservative was not banned from all childhood vaccines.


The truth is that Thimerosal is still present in a number of influenza vaccines that are administered to millions of pregnant women and young children each year. The CDC’s continued insistence that Thimerosal is safe in low doses challenged Dr. Geier to prove the validity of this claim. One of his most recent papers published in 2014, “A Case-Control Study Evaluating the Relationship Between Thimerosal-Containing Haemophilus Influenza Type B Vaccine Administration and the Risk for a Pervasive Developmental Disorder Diagnosis in the United States,” evaluated this relationship in children diagnosed with pervasive developmental disorders (PDD) who received Thimerosal-containing haemophilus influenza vaccine within the first 15-months of life. Haemophilus, often referred to as Hib, is caused by bacteria and can lead to pneumonia, throat swelling, infections and even death.

To conduct his study, Dr. Geier collected information from a PDD case group and a control group to determine which experienced greater exposure to organic mercury from Thimerosal-containing vaccinations in early childhood. Using statistic modeling methodology, Geier compared the data collected from three different test groups that received varying amounts of Thimerosal at different stages of early childhood (all within 15 months of birth).

Unlike several previous epidemiological studies, Geier’s research did find a significant relationship between organic mercury exposure from Thimerosal-containing childhood vaccines and the risk of child being subsequently diagnosed with a PDD. Even when test subjects were divided by gender, the results still clearly indicated that children diagnosed with PDD were more likely to have had higher exposure to Thimerosal through the Hib vaccine. Such strongly suggests that the presence of Thimerosal can indeed negatively impact the neurological development of its recipients.

There’s no denying that vaccinations play an important role in the health and well-being of the public by largely preventing the spread of deadly diseases. However, vaccinations should only protect individuals from harm, not inflict it upon them. When vaccinations present potentially dangerous risks to recipients, it’s time for reevaluation, and Dr. Geier’s latest research has shown us just that.

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