Thimerosal Fact Sheet

What is thimerosal?
  • It is a preservative used in 30 types of vaccines for 60 years.
  • Used in multi-dose vials, it prevents bacterial and fungal contamination.
  • It contains ethylmercury, a form of mercury that is probably less toxic and cleared faster from the body than methylmercury, the type of mercury found in some fish (swordfish, tuna).

Does the Influenza vaccine contain thimerosal?
  • The Influenza vaccine is being manufactured in both single doses that do not contain thimerosol and multi-dose vials that do contain thimerosol. The nasal version of the vaccine does not contain thimerosal.

When was thimerosal removed from childhood vaccines and why?
  • In 1999, when the presence of thimerosal in vaccines was highlighted in a report by the U.S. Food and Drug Administration. It was felt that if children received thimerosol in multiple different vaccines, the total amount of mercury they would be exposed to would be more than the amount recommended for their age.
  • Back when the initial concerns were raised, the studies disproving the association between thimerosal and autism had not been performed.
  • Since 2002, all recommended childhood vaccines have been thimerosal-free except for influenza vaccine for children over 3.

Isn’t it against California Law to give a child under 3 a vaccine containing thimerosal?
  • Thimerosal-containing vaccines may be unavoidable in epidemics and in other situations where multi-dose vials are needed.
  • Since 2004, when AB 2942 was signed into law, pregnant women and children under the age of three have only received thimerosal free vaccines. When the supply of a vaccine is limited, the Secretary of the California Health and Human Services Agency can grant an exemption to AB 2942 allowing pregnant women and young children to be given thimerosal containing vaccines. This happened during the H1N1 Influenza Epidemic.

Is thimerosal Associated with Autism?
  • Thimerosal was removed from all pediatric vaccines in 2001 and since 2004 no pregnant woman in California has received a thimerosal containing vaccine, yet the rate of autism remains unchanged.
  • The original studies that raised questions about the thimerosal-autism link have since been discredited and ten convincing studies have been published in leading medical journals indicating there is no link between vaccines and autism.

Where Can I Find Additional Information?  
There are no known risks of thimerosal when given in vaccines,
but there ARE risks of not vaccinating.