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Frequently Asked Questions about Thimerosal-free Vaccines

Which childhood vaccines do not contain thimerosal?
Today, with the exception of some influenza vaccine, none of the vaccines used to protect preschool children against 14 infectious diseases contain thimerosal as a preservative. (Those with a concentration of less than 0.0002% contain what is considered “trace,” or insignificant, amounts.) Certain Influenza (flu) vaccines and tetanus-diphtheria vaccines (Td) given to children age 7 and older contain thimerosal as a preservative. For more information on thimerosal content in some currently manufactured U.S. licensed vaccines, visit Thimerosal in Vaccines.

Why does some flu vaccine contain thimerosal?
Influenza (flu) vaccine is a new addition to the recommended childhood immunization schedule. In 2004, CDC added the vaccine to the childhood immunization schedule, recommending that children 6–23 months of age be vaccinated against flu each year. Inactivated influenza vaccine for children 6–23 months of age is currently available both with thimerosal as a preservative and preservative-free. For more information, see Thimerosal in Seasonal Flu Vaccine.

The removal of thimerosal as a preservative from influenza vaccine is a complicated process. The total amount of flu vaccine without thimerosal as a preservative will increase as vaccine manufacturing capabilities are expanded. In the meantime, it is important to keep in mind that the benefits of influenza vaccination outweigh the theoretical risk, if any, for exposure to thimerosal. Each year, an average of about 36,000 people in the United States die from influenza, and 114,000 have to be admitted to the hospital as a result of influenza. People aged 65 years and older, people of any age with chronic medical conditions, and very young children are more likely to get complications from influenza.

Why weren't thimerosal-containing vaccines taken off the market?
Scientific data have not established that vaccines containing thimerosal, used as a preservative, create an imminent or substantial hazard to public health or are in violation of U.S. Food and Drug Administration (FDA) laws or regulations, and therefore do not justify such a recall. A mandatory recall requires that the product present “an imminent or substantial hazard to the public health.” The FDA is responsible for voluntary and mandatory recalls of drug and vaccine products. The FDA continuously monitors the safety of these products.

Should immunization providers stop using licensed pediatric vaccines that contain thimerosal?
No. Immunization providers should use the vaccines available in their stock. The use of vaccines should continue according to the currently recommended schedule. The risks of not vaccinating children on time are significant, whereas the risks of thimerosal-containing vaccines have not been proven scientifically. Furthermore, availability of any vaccine containing thimerosal preservative is rare.

Are older lots of pediatric vaccines that contain thimerosal still being used?
With the exception of some influenza vaccines and tetanus-diphtheria (Td) vaccines (given to children aged 7 and older), the last lots of recommended childhood vaccines which contained thimerosal as a preservative expired by early 2003. If providers have such expired vaccines, they should discard them.

What is the availability of the thimerosal-free hepatitis B vaccine?
All hepatitis B vaccines intended for use in infants and children are free of thimerosal as a preservative, and an adequate supply of these vaccines is available for all infant and childhood vaccinations. This vaccine should be administered to all newborn infants and is a major cornerstone in the prevention of a potentially fatal disease in children and adults.


Please see References for a list of data sources for this information.

Page last reviewed: September 24, 2008
Page last updated: March 7, 2008
Content source: Immunization Safety Office, Office of the Chief Science Officer
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