Fact: Only one routine childhood vaccine still contains mercury, and it’s in a form that was never harmful anyway.

Antivax Myth: Vaccines contain toxic mercuryWhy the Myth Exists

Thimerosal (A.K.A. thiomersal) is a mercury-containing preservative used in multi-dose vials of vaccines. Using the concept of the precautionary principle, and in order to increase public confidence in the safety of vaccines, the U.S. Public Health Service, Centers for Disease Control, and American Academy of Pediatrics determined that thimerosal should be removed from all childhood vaccines.

This instead led some parents to suspect that thimerosal was a cause of autism.

Variations on this Myth

  • Thimerosal causes autism.
  • Mercury of any kind and dosage is harmful to humans.
  • Vaccinated children need to undergo a therapy called chelation to remove mercury.

Examples Found Online

The Real Deal: What the Evidence Shows

Most childhood vaccines never contained any form of mercury. The form of mercury that was used in some vaccines (hepatitis B, DTaP, and Hib) was ethylmercury, as opposed to methylmercury.

Methylmercury is indeed a significant health and environmental concern. Large quantities of it can be toxic to our nervous systems. But it is everywhere in the environment. We are exposed to it in minute quantities every day. If it enters the body, it is excreted back out slowly. It has been known to bioaccumulate—that is, it is absorbed by the body at a faster rate than it is lost. This is the compound we want to avoid in the excessive consumption of certain fish species. However, in tiny quantities it is found even in breast milk and is not harmful at that rate.

Ethylmercury is the only form of mercury that has ever been been associated with vaccines. Once thimerosal is injected into the body, it rapidly dissociates (breaks down) into ethylmercury and thiosalicylate. Ethylmercury is excreted from the brain, blood, and body much more quickly than methylmercury. It does not bioaccumulate like methymercury does. Thimerosal is also used as a preservative in tattoo ink.

Thimerosal helps prevent the growth of bacteria and fungi in vials of vaccines that are used for multiple doses. These infectious agents can cause severe disease and sometimes death. The ethylmercury that was an is included in some vaccines is in very tiny quantities, which even a newborn can metabolize and excrete in full quickly. Its sole ill effect is minor redness or swelling at the injection site.

The precautionary principle is the idea that there is no harm in exercising caution even if it later turns out to be unnecessary. In this case, the concept backfired because instead of increasing public confidence, the actions taken implied that vaccines were somehow dangerous.

Thimerosal has been removed from all routine childhood vaccines in the United States since 2001, except for multi-dose inactivated-virus preparations for influenza. Thimerosal-free versions of the influenza vaccine are available.

The removal of thimerosal from vaccines was done in the absence of data showing harm. At the time, no studies had shown any toxicity created by the ethylmercury exposure from multiple vaccines. However, there had been research for decades showing its safety.

Now more data is in. Numerous studies across multiple countries have demonstrated that the chances of developing autism is the same in children who have or have not been given vaccines containing thimerosal. Three studies have found that thimerosal in vaccines didn’t cause any hint of mercury toxicity. The signs of autism are significantly different from the signs of mercury toxicity.

Celation therapy is used in cases of true heavy metal toxicity. It is a risky procedure that should only be done by qualified medical personnel. It is never an appropriate therapy for autism nor for so-called detox after vaccination.

Vaccines do not cause autism.


“Is There Mercury in Vaccines?” [2:50]

Paul A. Offit, MD, explains the different types of mercury and how they are processed in the human body. He also discusses which commonly recommended infant vaccines still contain mercury-associated preservatives.

References and Further Reading


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