Background

In 2000, the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH) asked the Institute of Medicine (IOM) to establish an independent expert committee (the Immunization Safety Review Committee) to evaluate evidence regarding whether vaccines cause certain health problems, and to report their conclusions and recommendations.

In its first two reports (published in 2001), the committee examined evidence related to: 1) the theory that MMR (measles-mumps-rubella) vaccine causes autism and 2) the theory that vaccines containing the preservative thimerosal cause neurodevelopmental disorders, including autism, attention deficit hyperactivity disorder (ADHD), and speech or language delay. In the May 2004 report, the committee updates its conclusions and recommendations regarding vaccines and autism based on the significant number of studies that have been done on these topics since 2001.

CDC and NIH welcome this IOM report as a helpful contribution to the complex scientific issues related to autism.

Key Conclusions

The IOM Immunization Safety Review Committee’s most notable conclusions were:

• neither thimerosal-containing vaccines or MMR vaccine are associated with autism.
• the hypotheses regarding a link between autism and MMR vaccine and thimerosal-containing vaccines lack supporting evidence and are only theoretical.
• future research to find the cause of autism should be directed toward other promising lines of inquiry that are supported by current knowledge and evidence and offer more promise for providing an answer.

The committee’s conclusion that MMR vaccine is not associated with autism is consistent with their previous report on the topic. The committee’s conclusion in the 2004 report that thimerosal-containing vaccines are not associated with autism differs from their conclusion in 2001. At that time, the committee determined that there was not enough evidence to determine whether thimerosal was associated with neurodevelopmental disorders such as autism. The 2004 report explains that in 2001 there were no published epidemiological studies examining the potential association between thimerosal-containing vaccines and neurodevelopmental disorders. Since 2001, several studies have been published which the committee states “consistently provided evidence of no association."

Key Recommendations

The committee made a number of recommendations in the areas of policy, surveillance, and epidemiologic research, clinical studies, and communication, including:

• The committee does not recommend a policy review of the licensure of MMR vaccine or of the current schedule and recommendations for giving the MMR vaccine to children.
• The committee does not recommend a policy review of the current schedule and recommendations for the administration of routine childhood vaccines based on hypotheses regarding thimerosal and autism.
• The committee recommends that cost-benefit assessments regarding the use of thimerosal-containing versus thimerosal-free vaccines and other biological or pharmaceutical products, whether in the United States or other countries, should not include autism as a potential risk.
• The committee recommends developing programs to increase public participation in vaccine safety research and policy decisions and to enhance the skills and willingness of scientists and government officials to engage in constructive dialogue with the public about research findings and their implications for policy development.

Next Steps

The Committee has made helpful recommendations about policy and research in the areas of vaccine safety and autism. These will be considered in depth by the Public Health Service (PHS) agencies and their advisory bodies. At this time, CDC is making no changes to the current childhood immunization schedule and recommendations based on hypotheses regarding vaccines and autism.

Autism research and monitoring will continue to be high priorities for CDC. Such efforts will be essential in answering key questions about whether autism is increasing over time, determining the cause(s) of this condition, and ultimately developing prevention strategies. In addition to these critical efforts, we also realize the need to act on existing science to improve the lives of children already living with this condition by promoting developmental screening and intervention.

This page last reviewed and modified on July 12, 2004