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Executive Summary
Pages 1-22

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From page 1...
... The Immunization Safety Review Committee reviewed the evidence regarding the hypothesis that multiple immunizations increase the risk for immune dysfunction. Specifically, the committee looked at evidence of potential biological mechanisms and at epidemiological evidence for or against causality related to rishfor infections, the autoimmune disease type I diabetes, and allergic disorders.
From page 2...
... . The scientific assessment has two components: an examination of the epidemiological and clinical evidence regarding a possible causal relationship between the immunization and the adverse event, and an examination of experimental evidence for any biological mechanisms relevant to the hypothesis.
From page 3...
... . Today, a healthy infant immunized in complete accord with the recommended childhood immunization schedule receives up to 15 doses of five vaccines to protect against seven diseases by 6 months of age and up to 20 doses of seven vaccines to protect against 11 diseases by 2 years of age.
From page 4...
... For example, the diphtheria and tetanus toxoids and pertussis vaccine would be considered to represent "multiple immunization." The committee restricted its considerations regarding causality to those vaccines used in the United States. Because immune system dysfunction is a broad term adverse outcomes can result from stimulation of harmful immune responses or suppression of beneficial immune responses the committee had to define it for the purposes of this study.
From page 5...
... , estimated incidence for the early 1990s in the United States locations range from 11.7 per 100,000 in Chicago to 17.8 per 100,000 in Allegheny County, Pennsylvania. Allergic Diseases Allergy is responsible for a variety of acute and chronic health problems, including anaphylaxis, rhinitis, asthma, and allergic eczema.
From page 6...
... Calculations reviewed by the committee (Kollman, 2001, Offit et al., 2002) suggest that the number of antigens contained in the complete set of vaccines that comprise the recommended childhood immunization schedule has actually decreased over the past 20 to 30 years, despite the increased number of vaccines and vaccine doses administered.
From page 7...
... Not yet clear is the role vaccines may have in directly altering the development of the immune system, or the relative contribution of immunization-related changes in the context of the hygiene hypothesis. Vaccine-induced immune responses may differ from those resulting from wild-type infection because of differences in context, including differences in their timing, either in terms of age at exposure or of the sequence of antigen exposure.
From page 8...
... Despite these variations and limitations, the overall findings from the studies consistently demonstrated either no effect or a beneficial effect of multiple immunizations on heterologous disease. Therefore, the committee concludes that the epidemiological and clinical evidence favors rejection of a causal relationship between multiple immunizations and an increased risk of heterologous infections.
From page 9...
... Given the design weaknesses in the observational studies, and a randomized trial study that does not support the risk factor most frequently implicated in the observational studies, the committee concludes that the epidemiological and clinical evidence is inadequate to accept or reject a causal relationship between multiple immunizations and an increased risk of allergic disease, particularly asthma. Biological Mechanisms Although biological data do not provide an independent basis for evaluating causality, they can help validate epidemiologically based conclusions for or against causal associations, such data can also guide further investigation when epidemiological evidence is inconclusive.
From page 10...
... Therefore, 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 crossreaction 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.
From page 11...
... 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.
From page 12...
... infant immunization schedule could possibly influence an individual's risk for heterologous infections. SIGNIFICANCE ASSESSMENT The committee's assessment of the significance of concerns about possible immune system dysfunctions took several factors into consideration: the burden of the possible adverse outcomes of autoimmune diseases such as type 1 diabetes and allergic diseases such as asthma, indications of the extent of the concern about multiple immunizations, and views regarding the framework for immunization policy-making.
From page 13...
... By issuing the recommendation above, the committee does not intend to signal concern about health consequences of the multiple immunizations in the recommended childhood immunization schedule. In fact, the committee does not recommend a policy review by the CDC's Advisory Committee on
From page 14...
... Instead, the committee encourages epidemiological studies on immunization safety conducted within the framework of ongoing research and surveillance programs on allergy, autoimmune disease, and vaccine safety, it also encourages additional basic research on the immune system and on allergy and autoimmune diseases. The committee emphasizes the need for continuing surveillance of vaccine recipients and possible adverse events.
From page 15...
... The committee recommends exploring surrogates for type I diabetes and clinical history of allergic diseases in existing cohort studies of variations in the immunization schedule. Communication Along with the increasingly complicated immunization schedule has come a dramatic increase in the complexity of immunization safety issues, and it appears that some people have redefined their conceptions of the related risks and benefits.
From page 16...
... SUMMARY A review of the possible biological mechanisms for any adverse effects of multiple immunization on immune function does not support the hypothesis that the infant immune system is inherently incapable of handling the numbers of antigens presented during routine immunization. A review of the clinical and epidemiological literature suggests that multiple immunizations do not lead to risk of infection or type 1 diabetes, and that the possible role in the risk of allergy is indeterminate.
From page 17...
... EXECUTIVE SUMMARY 17 TABLE ES-1 Biological Mechanisms for the Possible Role of Immunizations in Increasing the Risk of Immune Dysfunction Adverse Health Mechanism Outcome Committee Conclusion About the Weight of the Biological Evidence Theoretical only Weak Theoretical only Autoimmune disease Allergic disease Heterologous Infections Molecular mimicry Bystander effect Loss of protection induced by homologous infection Via the hygiene hypothesis Collective mechanist) possibilities Bystander effect Via the hygiene hypothesis Collective mechanist)
From page 19...
... EXECUTIVE SUMMARY 19 :~ : :-: :':IG :':':~.:I':'E:'I: 1:'1:':1'1:' 'LG'C:':':~V l - ~ ~ EN :G=~ L :':1' EL':':' I:':l'C:l':G':':':l'O':':':W:G~ it:':'=: V'!
From page 21...
... Lampert D Apparent decreased risk of invasive bacterial disease after heterologous childhood immunization.
From page 22...
... Karp CL. The germless theory of allergic disease: Revisiting the hygiene hypothesis.


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