Appendix A
Committee Conclusions and Recommendations from Previous Reports

MEASLES-MUMPS-RUBELLA VACCINE AND AUTISM

Conclusions

The committee concludes that the evidence favors rejection of a causal relationship at the population level between measles-mumps-rubella (MMR) vaccine and autistic spectrum disorders (ASD). However, this conclusion does not exclude the possibility that MMR vaccine could contribute to ASD in a small number of children.

The committee concludes that further research on the possible occurrence of ASD in a small number of children subsequent to MMR vaccination is warranted, and it has identified targeted research opportunities that could lead to firmer understanding of the relationship.

Recommendations

Public Health Response

The committee recommends that the relationship between the MMR vaccine and autistic spectrum disorders receive continued attention.

Policy Review

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.



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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders Appendix A Committee Conclusions and Recommendations from Previous Reports MEASLES-MUMPS-RUBELLA VACCINE AND AUTISM Conclusions The committee concludes that the evidence favors rejection of a causal relationship at the population level between measles-mumps-rubella (MMR) vaccine and autistic spectrum disorders (ASD). However, this conclusion does not exclude the possibility that MMR vaccine could contribute to ASD in a small number of children. The committee concludes that further research on the possible occurrence of ASD in a small number of children subsequent to MMR vaccination is warranted, and it has identified targeted research opportunities that could lead to firmer understanding of the relationship. Recommendations Public Health Response The committee recommends that the relationship between the MMR vaccine and autistic spectrum disorders receive continued attention. Policy Review 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.

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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders Research Regarding MMR and ASD The committee recommends the use of accepted and consistent case definitions and assessment protocols for ASD in order to enhance the precision and comparability of results from surveillance, epidemiological, and biological investigations. The committee recommends the exploration of whether exposure to MMR vaccine is a risk factor for autistic spectrum disorder in a small number of children. The committee recommends the development of targeted investigations of whether or not measles vaccine-strain virus is present in the intestines of some children with ASD. The committee encourages all who submit reports to VAERS of any diagnosis of ASD thought to be related to MMR vaccine to provide as much detail and as much documentation as possible. The committee recommends studying the possible effects of different MMR immunization exposures. The committee recommends conducting further clinical and epidemiological studies of sufficient rigor to identify risk factors and biological markers of ASD in order to better understand genetic or environmental causes. Communications The committee recommends that government agencies and professional organizations, CDC and the Food and Drug Administration (FDA) in particular, review some of the most prominent forms of communication regarding the hypothesized relationship between MMR vaccine and ASD, including information they provide via the Internet and the ease with which Internet information can be accessed.

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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders THIMEROSAL-CONTAINING VACCINES AND NEURODEVELOPMENTAL DISORDERS Conclusions The committee concludes that although the hypothesis that exposure to thimerosal-containing vaccines could be associated with neurodevelopmental disorders is not established and rests on indirect and incomplete information, primarily from analogies with methylmercury and levels of maximum mercury exposure from vaccines given in children, the hypothesis is biologically plausible. The committee also concludes that the evidence is inadequate to accept or reject a causal relationship between thimerosal exposures from childhood vaccines and the neurodevelopmental disorders of autism, ADHD, and speech or language delay. Public Health Response Recommendations Policy Review and Analysis The committee recommends the use of the thimerosal-free DTaP, Hib, and hepatitis B vaccines in the United States, despite the fact that there might be remaining supplies of thimerosal-containing vaccine available. The committee recommends that full consideration be given by appropriate professional societies and government agencies to removing thimerosal from vaccines administered to infants, children, or pregnant women in the United States. The committee recommends that appropriate professional societies and government agencies review their policies about the non-vaccine biological and pharmaceutical products that contain thimerosal and are used by infants, children, and pregnant women in the United States. The committee recommends that policy analyses be conducted that will inform these discussions in the future. The committee recommends a review and assessment of how public health policy decisions are made under uncertainty.

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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders The committee recommends a review of the strategies used to communicate rapid changes in vaccine policy, and it recommends research on how to improve those strategies. Public Health and Biomedical Research The committee recommends a diverse public health and biomedical research portfolio. Epidemiological Research The committee recommends case-control studies examining the potential link between neurodevelopmental disorders and thimerosal-containing vaccines. The committee recommends further analysis of neurodevelopmental disorders in cohorts of children who did not receive thimerosal-containing doses as part of a clinical trial of DTaP vaccine. The committee recommends conducting epidemiological studies that compare the incidence and prevalence of neurodevelopmental disorders before and after the removal of thimerosal from vaccines. The committee recommends an increased effort to identify the primary sources and levels of prenatal and postnatal background exposure to thimerosal (e.g., Rho (D) Immune Globulin) and other forms of mercury (e.g., maternal consumption of fish) in infants, children, and pregnant women. Clinical Research The committee recommends research on how children, including those diagnosed with neurodevelopmental disorders, metabolize and excrete metals— particularly mercury. The committee recommends continued research on theoretical modeling of ethylmercury exposures, including the incremental burden of thimerosal with background mercury exposure from other sources. The committee recommends careful, rigorous, and scientific investigations of chelation when used in children with neurodevelopmental disorders, especially autism.

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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders Basic Science Research The committee recommends research to identify a safe, effective, and inexpensive alternative to thimerosal for countries that decide they need to switch from using thimerosal as a preservative. The committee recommends research in appropriate animal models on the neurodevelopmental effects of ethylmercury.

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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders MULTIPLE IMMUNIZATIONS AND IMMUNE DYSFUNCTION Conclusions Scientific Assessment Causality Conclusions The committee concludes that the epidemiological evidence favors rejection of a causal relationship between multiple immunizations and an increase in heterologous infection. The committee concludes that the epidemiological evidence favors rejection of a causal relationship between multiple immunizations and an increased risk of type 1 diabetes. The committee concludes that the epidemiological evidence is inadequate to accept or reject a causal relationship between multiple immunizations and increased risk of allergic disease, particularly asthma. Biological Mechanisms Conclusions Autoimmune Disease In the absence of experimental or human evidence regarding molecular mimicry or mercury-induced modification of any vaccine component to create an antigenic epitope capable of cross-reaction with self epitopes as a mechanism by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an individual’s risk of autoimmunity, the committee concludes that these mechanisms are only theoretical. The committee concludes that there is weak evidence for bystander activation, alone or in concert with molecular mimicry, as a mechanism by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an individual’s risk of autoimmunity. In the absence of experimental or human evidence regarding loss of protection against a homologous infection as a mechanism by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an

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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders individual’s risk of autoimmunity, the committee concludes that this mechanism is only theoretical. In the absence of experimental or human evidence regarding mechanisms related to the hygiene hypothesis as a means by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an individual’s risk of autoimmunity, the committee concludes that this mechanism is only theoretical. Considering molecular mimicry, bystander activation, and impaired immunoregulation collectively rather than individually, the committee concludes that there is weak evidence for these mechanisms as means by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an individual’s risk of autoimmunity. Allergic Disease The committee concludes that there is weak evidence for bystander activation as a mechanism by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an individual’s risk of allergy. In the absence of experimental or human evidence regarding mechanisms related to the hygiene hypothesis as a means by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an individual’s risk of allergy, the committee concludes that this mechanism is only theoretical. The committee concludes that there is weak evidence for the existence of any biological mechanisms, collectively or individually, by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an individual’s risk of allergy. Heterologous Infection The committee concludes that there is strong evidence for the existence of biological mechanisms by which multiple immunizations under the U.S. infant immunization schedule could possibly influence an individual’s risk for heterologous infections. Significance Assessment The committee concludes that concern about multiple immunizations has been, and could continue to be, of societal significance in terms of parental worries, potential health burdens, and future challenges for immunization policymaking.

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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders Public Health Response Recommendations Policy Review The committee recommends that state and federal vaccine policymakers consider a broader and more explicit strategy for developing recommendations for the use of vaccines. The committee does not recommend a policy review—by the CDC’s Advisory Committee on Immunization Practices (ACIP), the American Academy of Pediatrics’ Committee on Infectious Diseases, and the American Academy of Family Physicians—of the current recommended childhood immunization schedule on the basis of concerns about immune system dysfunction. The committee does not recommend a policy review by the Food and Drug Administration’s Vaccines and Related Biologic Products Advisory Committee of any currently licensed vaccines on the basis of concerns about immune system dysfunction. Research Epidemiological Research The committee recommends exploring the feasibility of using existing vaccine surveillance systems, alone or in combination, to study safety questions related to asthma and other important allergic disorders, as well as to type 1 diabetes and other important autoimmune diseases. The committee recommends exploring the use of cohorts for research on possible vaccine-related disease risks. Furthermore, the committee recommends that disease registries and research programs for autoimmune and allergic disorders routinely collect immunization histories as part of their study protocol. Basic Science and Clinical Research The committee recommends continued research on the development of the human infant immune system. The committee endorses current research efforts aimed at identifying genetic variability in human immune system development and immune system

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Immunization Safety Review: Hepatitis B Vaccine and Demyelinating Neurological Disorders responsiveness as a way to gain a better understanding of genetic susceptibility to vaccine-based adverse events. The committee recommends exploring the feasibility of collecting data on surrogate markers for autoimmune and allergic disorders in the vaccine testing and licensing process. The committee recommends exploring surrogates for allergy and autoimmunity in existing cohort studies of variations in the vaccine schedule. Communication The committee recommends that an appropriate panel of multidisciplinary experts be convened by the Department of Health and Human Services. It would develop a comprehensive research strategy for knowledge leading to the optimal design and evaluation of vaccine risk-benefit communication approaches.