Mercury and Vaccines (Thimerosal) : Part 3

by CDC

(Page 3 of 3)

In the second analysis, the authors looked at the estimated amount of mercury exposure from vaccines over time and the number of children enrolled in U.S. special education programs for selected disabilities. The authors present figures with very high correlations, but from the limited description provided, it does not seem that the appropriate data were available to perform the analyses and derive the conclusions that the authors report. Although enrollment in special education of children with autism did increase during the 1990's, it has not been determined whether this represents a real increase in the incidence of autism as opposed to increased awareness and acceptance of the diagnosis, better recognition, changing diagnostic criteria, or educational and service incentives to make the diagnosis.

Great Britain experienced a rapid rise in autism among children born in the 1980's and early 1990's. Could this be due to thimerosal in vaccines?

It is unlikely that the rapid increase in autism cases in the UK was due to thimerosal. The only vaccine in the UK's childhood immunization program that contains thimerosal is DTP. All other vaccines (OPV, BCG, MMR, Hib, menC) added to the program since the 1950's are and have always been thimerosal free. In addition, if thimerosal in vaccines were causing autism, we would expect to see a simultaneous increase in both thimerosal exposure and autism cases. However, from the 1950's on, there was no increase in the amount of thimerosal UK children were receiving from vaccines, yet there was a jump in autism cases in the 1980's.

A significant change in the UK's program did occur in 1990 when they accelerated their immunization schedule so vaccines would be given earlier (changed from 3, 5, and 8 months to 2, 3 and 4 months). However, the rate of autism was rising long before this change occurred.

I understand some people are sensitive to mercury and must avoid it. Do they have problems with thimerosal-containing vaccines?

Some individuals experience local skin reactions such as redness and swelling that may suggest a delayed-type of minor allergic reaction following injection with products containing thimerosal. Research suggests that most people who have a contact or skin allergy to thimerosal will not have the reaction when thimerosal is injected under the skin. A prior history of a minor reaction to thimerosal in a vaccine is not considered a contraindication to further vaccination with thimerosal-containing vaccines. Severe anaphylactic (allergic) reaction to any vaccine is a contraindication to further vaccination with the vaccine.

Do measles, mumps, and rubella (MMR) vaccines contain thimerosal?

No, MMR vaccine does not and never did contain thimerosal. Varicella (chickenpox), inactivated polio (IPV), and pneumococcal conjugate vaccines have also never contained thimerosal.

Do all flu vaccines contain thimerosal?

No. Influenza vaccine is currently available both with thimerosal as a preservative and preservative-free. For the 2004-05 influenza season, it is likely that 6-8 million doses of inactivated influenza vaccine without thimerosal as a preservative will be available. This represents a substantial increase in the available amount of inactivated influenza vaccine without thimerosal as a preservative, compared with about 3.2 million doses that were available during the 2003-04 influenza season.

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 be increased 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 age 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 are chemicals and other substances added to vaccines?

Many foods and medicines, including vaccines, have chemicals added to them to prevent the growth of germs, reduce spoilage, and prevent it from losing its potency over time.

Some additives are used in the production of vaccines. Vaccines may include suspending fluid (e.g., sterile water, saline, or fluids containing protein); preservatives and stabilizers (e.g., albumin, phenols, and glycine); and adjuvants, or enhancers, that help the vaccine improve its immunogenicity (ability to protect against disease).

About the Author

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The Centers for Disease Control and Prevention (CDC) is one of the 13 major operating components of the Department of Health and Human Services (HHS), which is the principal agency in the United States government for protecting the health and safety of all Americans and for providing essential human services, especially for those people who are least able to help themselves.