CDC's Statement on Thimerosal

The Center for Disease Control responds to questions about thimerosal in flu vaccines.

Posted on

The Doctor Oz Show Asks: What is the CDC’s response to the new book by Robert F. Kennedy Jr and Dr. Mark Hyman calling for the removal of Thimerosal from all flu vaccines?

Thimerosal has been used safely in vaccines for over 70 years and has a proven track record of being safe. A variety of scientists have been studying the use of vaccines that have thimerosal in them for many years. They haven’t found any actual evidence that thimerosal causes harm.  The many federal partners involved in immunizations have closely followed and evaluated the scientific discussion on thimerosal and are well aware of the significant amount of information that has been generated in addressing this question. In addition to a thorough review of the evidence we sought the input of the independent Institute of Medicine on this issue. The conclusion of the scientific community is clear that thimerosal-containing vaccines are safe and effective and do not represent a public health risk. Thimerosal is used as a preservative in a number of biological and drug products, including many vaccines, to help prevent potentially life threatening contamination with harmful microbes.

The Doctor Oz Show Asks: Why was Thimerosal removed from all mandatory childhood vaccines, but still remains in multi-dose flu vaccines recommended and given to pregnant women and children?

In 1999, the Food and Drug Administration (FDA) was required by law to assess the amount of mercury in all the products the agency oversees, not just vaccines. The U.S. Public Health Service decided that as much mercury as possible should be removed from vaccines, and thimerosal was the only source of mercury in vaccines.  Although no evidence suggests that there are safety concerns with thimerosal, vaccine manufacturers removed it from childhood vaccines in 2001 as a precautionary measure. It’s also important to point out the difference between ethylmercury (what is found in the thimerosal preservative) and methylmercury (the metal naturally found in the environment and in some types of fish and food).

To produce enough flu vaccine for the entire country, some of it must be put into multi-dose vials. These vials have very tiny amounts of thimerosal in them that is used as a preservative. This is necessary because each time an individual dose is drawn from a multi-dose vial with a new needle and syringe, there is the potential to contaminate the vial with harmful microbes (bacteria and other environmental contaminants). So, this preservative is needed as a safeguard to prevent contamination of the vial when individual doses are drawn from it, and keep people who are receiving the flu shot from the multi-dose vial safe. Children can safely receive flu vaccine that contains thimerosal.

Today, childhood vaccines that used to contain thimerosal as a preservative are now put into single-dose vials or syringes, with the exception of the multi-dose vials of flu vaccine, so no preservative is needed. Nearly 2/3 of the flu vaccine that is manufactured for the United States is thimerosal-free. Parents can also ask their healthcare provider to receive a thimerosal-free version of the flu vaccine.

Helpful resources:
CDC’s frequently asked questions about thimerosal
CDC’s thimerosal website
Complete list of vaccines and their thimerosal content level