Immunization Safety Review Measles-Mumps-Rubella Vaccine and Autism
Marie McCormick, M.D., Sc.D.
Chairman of the Immunization Safety Review Committee
Institute of Medicine/National Academy of Sciences
Professor and Chair, Department of Maternal and Child Health
Harvard School of Public Health
Committee on Government Reform
U.S. House of Representatives
April 25, 2001
Good morning, Mr. Chairman and members of the committee, my name is Marie McCormick. I am a professor and chair of the Department of Maternal and Child Health at Harvard School of Public Health. I chair the Institute of Medicine Committee on Immunization Safety Review, which released its report on Measles-Mumps-Rubella Vaccine and Autism on Monday, April 23. I appreciate the opportunity to provide testimony to you based on the findings of this report. A copy of my testimony and the Executive Summary have been submitted for the record. Dr.William Colglazier, Executive Officer of the National Academy of Sciences and Ms. Susanne Stoiber, Executive Officer of the Institute of Medicine accompany me.
The genesis of this report was a December 1999 discussion between the CDC and the IOM regarding the need for an independent group to examine vaccine-safety concerns. The CDC and NIH formally engaged the services of the Institute of Medicine (IOM) in September 2000, which in turn appointed the Committee in November 2000. The committee is comprised of 15 members with expertise in pediatrics, immunology, neurology, infectious disease, epidemiology, biostatistics, public health, genetics, ethics, and risk perception and communication. To preclude any real or perceived conflicts of interest, committee members were subject to strict selection criteria that excluded anyone who had participated in research on vaccine safety, received funding from vaccine manufacturers or their parent companies, or served on vaccine advisory committees.
The committee is charged with examining three vaccine safety issues each year for 3 years. The committee was asked to assess the scientific plausibility of the safety concern, the significance of the issue in a broader social context, and to suggest appropriate actions. The first hypothesis the committee was asked to consider is the linkage between measles-mumps-rubella vaccine (MMR) and autism.
Study Background and Methodology
The MMR vaccine has been extremely successful in virtually eliminating measles, mumps, and rubella in the United States. Measles cases, for example, dropped from over 400,000 per year in the pre-vaccine era to only 100 in 1999.
Some are concerned though that the MMR vaccine might cause autistic spectrum disorders. These are incurable, permanent, and serious developmental problems in children. Scientists generally agree that most cases of autistic spectrum disorders result from events that occur in the prenatal period or shortly after birth. However, concern arises about MMR vaccine because autistic symptoms typically become evident in the child’s second year--about the same time the MMR vaccine is first administered.
A growing body of work has examined this subject. In a study published in The Lancet in 1998, researchers describe 12 children who developed behavioral problems including autism shortly after receiving the MMR vaccine. Since then, this group and others have further examined this potential relationship.
To evaluate the hypothesis on MMR vaccine and autistic spectrum disorders, the committee conducted an extensive review of the published, peer-reviewed scientific and medical literature. We held an open scientific meeting including a broad group of researchers and vaccine safety advocates. Finally, a working group of the committee conferred with parents of autistic children and vaccine safety advocates to discuss their concerns.
The Committee concludes that the evidence favors rejection of a causal relationship at the population level between MMR vaccine and autistic spectrum disorders. The committee bases this conclusion on the following evidence:
• A consistent body of epidemiological evidence shows no association at a population level between MMR vaccine and autistic spectrum disorders.
• The original case series of children with autistic spectrum disorders and bowel symptoms and other available case reports are uninformative with respect to causality.
• Biologic models are fragmentary.
• There is no relevant animal model.
However, the committee notes that its conclusion does not exclude the possibility that MMR vaccine could in rare cases contribute to autistic spectrum disorders resulting in a very small number of affected children. This possibility arises because the epidemiological evidence lacks the precision to assess rare occurrences and the proposed biological models, although far from established, are nevertheless not disproved.
In its significance assessment, the committee considered the burden of measles, mumps, and rubella infections, the burden of autistic spectrum disorders, and the level of public concern. Measles, mumps, and rubella can lead to significant morbidity and mortality and treatment of these diseases is limited.
Outbreaks of measles, mumps, or rubella disease could easily occur now were MMR immunization rates to decline as a result of fears about MMR. Yet, because MMR vaccine is a mandatory vaccine that is administered to healthy children--in part, as a public health measure to protect others--the responsibility of the government to ensure the safety of this vaccine is high. The burden of autism, an incurable and serious disorder, requires consideration of all possible etiologies. In addition, the level of public concern about MMR vaccine safety is high.
Because of the limitations of the evidence, the significant public concern surrounding the issue, the risk of disease outbreaks if immunization rates fall, and the burden of autism, the committee recommends that further attention be given to this matter.
Specific recommendations regarding policy review, research and surveillance, and communication follow.
• The committee does not recommend a policy review at this time of the licensure of MMR vaccine or of the current schedule and recommendations for administration of MMR vaccine.
Research Regarding MMR and Autistic Spectrum Disorders
The committee concludes that further targeted research on the possible contribution of MMR vaccine to autistic spectrum disorders in some children is warranted For example:
• Use accepted case definitions and assessment protocols for autistic spectrum disorders to enhance the precision and comparability of research results.
• Explore whether exposure to MMR vaccine is a risk factor for autistic spectrum disorders in some children.
• Explore whether measles vaccine-strain virus is present in the intestines of some autistic children.
• Encourage all who submit reports to the Vaccine Adverse Event Reporting System about MMR vaccine and autism to provide as much detail and documentation as possible.
The committee heard from parents that obtaining unbiased and accurate information on the possible relationship between MMR vaccine and autistic spectrum disorder has been difficult. The Committee recommends:
• · That governmental and professional organizations, CDC and the Food and Drug Administration (FDA) in particular, review some of the most prominent forms of communication regarding the relationship between MMR vaccine and autistic spectrum disorder. Direct input from parents and other stakeholders would be invaluable in conducting an evaluation of communication tools.
In its discussion of recommendations, the committee identified more general concerns that it could not adequately address in this report. It intends to address these in the future.
This concludes my oral statement. I am happy to answer any questions.