Health In Focus
Highlights:
  • Thimerosal is a preservative in multi-dose vaccines
  • It contains a form of mercury called ethylmercury, which is different from methylmercury that causes mercury-related toxicity
  • It does not appear to be associated with autism

Thimerosal, a mercury-containing preservative used in multi-dose vaccines, does not appear to cause autism in children.

Vaccines are used to prevent infectious diseases, and therefore, it is only natural that people would expect minimal side effects with their use. They are routinely administered to children to improve their immunity and protect them from a host of infectious diseases that were once responsible for a high infant and childhood mortality rate. Vaccines are commonly used in adults as well.
Thimerosal in Vaccines Does Not Cause Autism in Children

Multi-dose vaccines can be administered to several individuals over a period of time, when stored under proper conditions. They are often more cost effective when compared to single-dose vaccines, especially when used to vaccinate large communities.


Multi-dose vaccines require a preservative to prevent introduction of infections into the vaccine during repeat aspiration. One particular incident in the year 1928 highlighted the importance of adding a preservative to such vaccines. Several children who received diphtheria vaccine from a multi-dose preparation a few days after it was initially used, died following the vaccination, most likely due to the introduction of infection into the vaccine by the needles used to draw the vaccine.

The mercury-containing thimerosal was the chosen preservative. It prevents bacterial and fungal contamination of the vaccine but does not add to the activity of the vaccine against disease.

Over the years, it came to be known that mercury can cause nervous tissue-related side effects. It can also damage the brain and cause conditions like autism. Therefore, the use of the mercury-containing thimerosal in a vulnerable child with a growing brain without any illness did raise questions about the addition of the compound to vaccines. As a consequence, thimerosal was removed from most vaccines as a precautionary measure in the United States and is now present mainly in some multi-dose flu vaccines. However, it continues to be used in several other countries.

Researchers feel that the fears about thimerosal causing conditions like autism are not substantiated. Unlike the brain-damaging mercury compounds that contain methylmercury, thimerosal is broken down to ethylmercury in the body, which is eliminated faster from the body. Studies have also failed to demonstrate a decline in the number of autism cases after reducing the use of thimerosal in vaccines, demonstrating that thimerosal has nothing to do with the development of autism.

Thus, if your child's vaccine does contain thimerosal, you need not worry about it. It is more important to protect your child from the potentially deadly effects of the infection that he might be exposed to. If you are still concerned, you could ask your child's pediatrician to use a vaccine that does not contain thimerosal.

References :
  1. Thimerosal in Vaccines - (http://www.cdc.gov)
  2. Thimerosal and Vaccines - (https://www.fda.gov/biologicsbloodvaccines/safetyavailability/vaccinesafety/ucm096228.htm)
Source: Medindia

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