Primary Navigation for the CDC Website
CDC en EspaƱol
Vaccine Safety
divider
E-Mail Icon E-mail this page
Printer Friendly Icon Printer-friendly version
divider
 Vaccine Safety Basics
bullet Information for Parents
bullet Why It's Important to Monitor Vaccine Safety
bullet How Vaccines Are Tested and Monitored
bullet Common Questions
bullet Vaccine Safety Concerns
  bullet Human Papillomavirus (HPV) Vaccine
bullet MMR Vaccine
bullet Mercury and Vaccines (Thimerosal)
bullet Questions About Multiple Vaccines
bullet Questions About Vaccine Recalls
bullet Fainting (Syncope) After Vaccination
bullet Kawasaki Syndrome and RotaTeq Vaccine
bullet GBS and Menactra Meningococcal Vaccine
bullet Sudden Infant Death Syndrome
bullet Hepatitis B Vaccine and Concerns about Multiple Sclerosis
bullet History of Vaccine Safety

 Public Health Activities
bullet Vaccine Adverse Event Reporting System (VAERS)
bullet Vaccine Safety Datalink (VSD) Project
bullet Clinical Immunization Safety Assessment (CISA) Network
bullet Brighton Collaboration
bullet Vaccine Technology
bullet Emergency Preparedness
bullet Publications
bullet Scientific Agenda

Mercury and Vaccines (Thimerosal)

Photo of bottle

Thimerosal is a mercury-containing preservative used in some vaccines and other products since the 1930s. There is no convincing scientific evidence of harm caused by the low doses of thimerosal in vaccines, except for minor reactions like redness and swelling at the injection site. However, in July 1999, the Public Health Service agencies, the American Academy of Pediatrics, and vaccine manufacturers agreed that thimerosal should be reduced or eliminated in vaccines as a precautionary measure.

Since 2001, with the exception of some influenza (flu) vaccines, thimerosal is not used as a preservative in routinely recommended childhood vaccines.

For more information, please see Infant and Environmental Exposures to Thimerosal and Neuropsychological Outcomes at Ages 7 to 10 Years.

CDC Statement on Autism and Thimerosal

As the country's leading public health agency, the Centers for Disease Control and Prevention (CDC) is committed to protecting the health of all Americans—including infants, children, and adolescents. CDC shares with parents and many others great concern about the number of children with autism spectrum disorders (ASD). We are committed to understanding what causes autism, how it can be prevented, and how it can be recognized and treated as early as possible.

Photo of group of kids

Recent estimates from CDC's Autism and Developmental Disabilities Monitoring network found that about 1 in 150 children have an ASD. This estimate is higher than estimates from the early 1990s. Some people believe increased exposure to thimerosal (from the addition of important new vaccines recommended for children) explains the higher prevalence in recent years. However, evidence from several studies examining trends in vaccine use and changes in autism frequency does not support such an association. Furthermore, a scientific review* by the Institute of Medicine (IOM) concluded that "the evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism." CDC supports the IOM conclusion.

CDC recognizes that autism is an urgent health concern and supports comprehensive research as our best hope for understanding the causes of autism and other developmental disorders. Through collaborations with partners in government, research centers, and the public, CDC is focusing on three areas—

  1. Understanding the frequency and trends of autism spectrum disorders.
  2. Advancing research in the search for causes and effective treatments.
  3. Improving early detection and diagnosis so affected children are treated as soon as possible.

Related Links

Related Research

McMahon AW, Iskander JK, Haber P, Braun MM, Ball R. Inactivated influenza vaccine (IIV) in children <2 years of age: Examination of selected adverse events reported to the Vaccine Adverse Event Reporting System (VAERS) after thimerosal-free or thimerosal-containing vaccine. Vaccine 2008;26(3):427–429.

*Links to non-Federal organizations found at this site are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization Web pages found at these links.

Page last reviewed: June 23, 2008
Page last updated: February 8, 2008
Content source: Immunization Safety Office

  Home | Policies and Regulations | Disclaimer | e-Government | FOIA | Contact Us
Safer, Healthier People

Centers for Disease Control and Prevention
1600 Clifton Rd, Atlanta, GA 30333, U.S.A.
Public Inquiries: 1-800-CDC-INFO (232-4636); 1-888-232-6348 (TTY)
USA.govDHHS Department of Health
and Human Services