Immunization Safety Review:
Measles-Mumps-Rubella Vaccine and Autism

 More on Immunization and Autism
 From: Steve Eidelman
 

 Immunization is widely regarded as one of the world's most effective tools
 for protecting public health. In the United States alone,
 child-vaccination programs have resulted in the elimination of smallpox and polio and
 rendered once-common, often debilitating, and potentially life-threatening
 infectious diseases--such as diphtheria, pertussis, and measles--exceedingly uncommon.

 But along with these benefits have come concerns about safety, making some
 immunization policies a subject of public debate. One such issue is
 whether or not the measles-mumps-rubella (MMR) vaccine causes autistic spectrum
 disorders (ASD), frequently referred to simply as autism.

 The MMR vaccine, which comprises three vaccines given in a single shot,
 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. However,
 these diseases remain a serious threat in other parts of the world where
 children are not routinely vaccinated. Measles alone resulted in over a million
 deaths in children around the world last year.

 Some parents and researchers are concerned though that the MMR vaccine
might cause ASD. Autistic spectrum disorders are incurable, permanent diseases
 that result in serious developmental problems in children. Although
 scientists generally agree that most cases of ASD result from events that
 occur in the prenatal period or shortly after birth, there is considerable
 concern because autistic symptoms typically do not emerge until the
 child's second year--about the same time the MMR vaccine is first administered. In
 addition, there are concerns that the introduction of wide-scale use of
 MMR coincides with an apparent increase in the incidence of autism.

 Recent research in Britain provides suggestive evidence of such a link. In
 a highly publicized study, published in The Lancet in 1998, researchers
 describe 12 children who developed behavioral problems, including ASD,
 shortly after receiving the MMR vaccine. While the authors note that their
 study did not prove an association between MMR and ASD, it suggests the
 need for further research on this hypothesis. Since then, this group and other
 scientists have further examined this potential relationship.

 The CDC and the National Institutes of Health recognized the need for an
 independent group to carefully examine the hypothesized MMR-autism link
 and address other vaccine-safety issues as well, in order to give some
 guidance to themselves, health care providers, researchers, and a concerned public.
 These agencies engaged the Institute of Medicine (IOM), which in turn
 appointed the Immunization Safety Review Committee, a 15-member body of
 health professionals with wide-ranging expertise in areas relevant to the
 problem. To preclude any real or perceived conflicts of interest,
 candidate 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 results of the committee's assessment of the
 issue are described in the report titled Immunization Safety Review:
 Measles-Mumps-Rubella Vaccine and Autism.

 The committee has reviewed the numerous research efforts on the MMR-autism
 hypothesis. "The evidence favors rejection of a causal relationship at the
 population level between MMR vaccine and autistic spectrum disorders," the
 committee concludes in its report. "A consistent body of epidemiological
evidence shows no association at a population level between MMR and ASD," the report says.

  Moreover, the committee can find no proven biological mechanisms that
 would explain such a relationship. Scientists have suggested some theories, but
 none have been demonstrated. For example, though it is possible that a
 viral infection caused by the vaccine could invade the central nervous system,
 provoke an autoimmune response and ultimately produce autism, researchers
 have observed no evidence of this kind of injury. Finally, scientists have not
 been able to make inferences by studying the hypothesis in laboratory
 animals because of the difficulty of mimicking these conditions in animals.

 Other leading medical groups--the American Academy of Pediatrics, the
 World Health Organization, and British health authorities--have come to similar
 conclusions for largely the same reasons.

 Though the MMR-autism question might appear to be resolved, science is
 always a work in progress; a conclusion is only as good as the methods of
 the analysis. The epidemiological studies, traditional public health tools
 used to examine the risk factors for a disease on a population level, were
 at a disadvantage here because there is little variation in exposure to
 MMR since children in most developed countries are vaccinated similarly.
 Furthermore, the difficulties in diagnosing and determining the exact
 onset of autism in children make it difficult to design appropriate studies and
 compare the results from those studies.

 The committee acknowledges they could not rule out another
 possibility--that MMR vaccine could contribute to ASD in a small number of children--because
 existing epidemiological tools may not have enough precision to detect the
 occurrence of rare effects like ASD.

 The significance of this set of issues transcends the science alone.
 Infectious diseases like measles, mumps, and rubella, left unchecked,
 could cause considerable sickness and death. Public-health officials fear a
 repetition of the pertussis-vaccine history of the 1970s, when the
 combination of low numbers of pertussis cases and public concerns about
 the vaccine's safety caused immunization rates around the world to plummet,
 with sobering results. In Japan, for instance, pertussis vaccine coverage
 dropped from 80% to 10% in the mid-1970's resulting in epidemic involving 13,000
 reported cases and 41 deaths. "Similar disease outbreaks could easily
 occur, with devastating effects," says the committee, "were immunization rates to
 decline as a result of fears regarding MMR vaccine."

 Still, "the responsibility of the government to ensure the safety of [the
 MMR] vaccine is high, even if the adverse outcome is rare," the committee
 notes. The seriousness of autism - an incurable and serious behavioral
 disorder - requires rigorous consideration of all possible etiologies. And
 in any case, it adds, the level of public concern about MMR vaccine safety
 is high and must be meaningfully addressed.

 This is especially important in that MMR vaccination is required by law in
 all 50 states for entry into school and day care, in part, to protect the
 health of others. These factors, the committee concludes, suggest the need
 for continued attention to this issue.

 At present, however, no change of MMR immunization procedures is warranted.
 The report plainly states that "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."

 The committee does propose targeted research efforts and more rigorous
 data-gathering procedures. These would give scientists a firmer
 understanding of MMR vaccination and any possible side effects. In
 particular, the committee recommends the use of common definitions for
 autism cases; more detail and documentation in their reporting; comparing
 the effects of different immunization exposures; and clinical and
 epidemiological studies to identify risk factors and biological markers of ASD.

 Further, the committee notes that government agencies responsible for
 immunization should recognize that most members of the public currently
 get their information on this and other health issues from the news media and
 the Internet. As a result, agencies such as the CDC and Food and Drug
 Administration must actively work at providing helpful public
 communications, beginning with the improved accessibility of their own Web sites.

 "Attention should be given to how the material is perceived and used by
 those with the right and desire to know--the parents of children about to
 be immunized or those who believe their child has been adversely affected,"
 the committee says. "Direct input from parents and other stakeholders would be
 invaluable in conducting a systematic and effective evaluation of current
 communication tools."

 Information on the Immunization Safety Review Committee can be found at
 www.iom.edu/ImSafety

 Copies of Immunization Safety Review: Measles-Mumps-Rubella Vaccine and
 Autism are available for sale from the National Academy Press; call (800)
 624-6242 or (202) 334-3313 (in the Washington metropolitan area), or visit
 the NAP home page.

 This study was funded by the Centers for Disease Control and Prevention
 and
 the National Institute of Allergy and Infectious Diseases of the National
 Institutes of Health as part of an National Institute of Health Task Order No. 74.

 The Institute of Medicine is a private, nonprofit organization that
 provides health policy advice under a congressional charter granted to the National
 Academy of Sciences. For more information about the Institute of Medicine,
 visit the IOM home page at ww.iom.edu.

 © 2001 by the National Academy of Sciences. All rights reserved.

 Permission is granted to reproduce this document in its entirety, with no
 additions or alterations.

 MARIE McCORMICK, M.D., Sc.D., (Chair), Professor and Chair, Department of
 Maternal and Child Health, Harvard School of Public Health
 RONALD BAYER, Ph.D., Professor, Division of Sociomedical Sciences, School
 of  Public Health, Columbia University
 ROSEMARY CASEY, M.D., Associate Professor of Pediatrics, Jefferson Medical
 College and Director, Lankenau Faculty Pediatrics, Wynnewood, Pennsylvania
 JOSHUA COHEN, Ph.D., Senior Research Associate, Harvard Center for Risk
 Analysis, Harvard School of Public Health
 VERNICE DAVIS-ANTHONY, M.P.H., Senior Vice President, Corporate Affairs
 and Community Health, St. John Health System, Detroit, MI
 BETSY FOXMAN, Ph.D., Professor, Department of Epidemiology, School of
 Public Health, University of Michigan
 CONSTANTINE GATSONIS, Ph.D., Professor of Medical Science and Applied Math,
 and Director, Center for Statistical Sciences, Brown University
 STEVEN GOODMAN, M.D., M.H.S., Ph.D., Associate Professor, Department of
 Oncology, Division of Biostatistics, Johns Hopkins School of Medicine
 ELLEN HORAK, M.S.N., Chief of Local Services, Office of Local and Rural
 Health, Kansas Department of Health and Environment
 MICHAEL KABACK, M.D., Professor, Pediatrics and Reproductive Medicine,
 University of California, San Diego
 Gerald Medoff, M.D., Professor, Department of Internal Medicine,
 Washington University School of Medicine
 REBECCA PARKIN, Ph.D., Associate Research Professor, Department of
 Occupational & Environmental Health, School of Public Health and Health
 Services, George Washington University
 BENNETT SHAYWITZ, M.D., Professor of Pediatrics and Neurology,
 Co-Director, Yale Center for the Study of Learning and Attention
 CHRISTOPHER WILSON, M.D., Professor and Chair, Department of Immunology,
 University of Washington
 ALFRED BERG, M.D., M.P.H., Professor and Chair, Department of Family
 Medicine, University of Washington School of Medicine is a member of the
 Immunization Safety Review Committee, but was unable to attend the meeting
 on the topic of this report.

 Health Promotion and Disease Prevention Board Liaison
 RICHARD B. JOHNSTON, Jr., M.D., Professor of Pediatrics, Department of
 Pediatrics, University of Colorado School of Medicine and National Jewish
 Medical & Research Center

 Staff
 KATHLEEN STRATTON, Ph.D., Study Director
 ALICIA GABLE, M.P.H., Program Officer
 PADMA SHETTY, M.D., Program Officer
 DONNA ALMARIO, Research Associate
 KYSA CHRISTIE, Research Assistant
 ANN ST. CLAIRE, Senior Project Assistant
 ROSE MARIE MARTINEZ, Sc.D., Director, Board on Health Promotion and
 Disease Prevention

 Steven M. Eidelman
 Executive Director
 The Arc of the United States
 1010 Wayne Avenue, Suite 650
 Silver Spring, MD 20910
 301-565-5469 - Phone
 301-565-3843 - Fax
 eidelman@thearc.org
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