findings are released to the public in a brief consensus report 60 to 90 days after its meeting.

The committee is charged with assessing both the scientific evidence regarding the hypotheses under review and the significance of the issues for society.

  • The scientific assessment has two components: (1) an examination of the epidemiologic and clinical evidence regarding a possible causal relationship between exposure to the vaccine and the adverse event; and (2) an examination of theory, and of experimental or observational evidence from in vitro, animal, or human studies, regarding biological mechanisms that might be relevant to the hypothesis.

  • The significance assessment addresses such considerations as the burden of the health risks associated with the adverse event as well as with the vaccine-preventable disease. Other considerations may include the perceived intensity of public or professional concern, and the feasibility of additional research to help resolve scientific uncertainty regarding causality.

The findings of the scientific and significance assessments underlie the committee’s recommendations regarding the public health response to the issue. In particular, the committee addresses any needs for a review of immunization policy, for current and future research, and for effective communication strategies. See Figure 1 for a schematic representation of the committee’s charge.

THE STUDY PROCESS

The committee held an initial organizational meeting in January 2001. CDC and NIH presented the committee’s charge at the meeting, and the committee then conducted a general review of immunization safety concerns. At this meeting, the committee also determined the basic methodology to be used for assessing causality in the hypotheses to be considered in its subsequent deliberations. A website (www.iom.edu/imsafety) and a listserv were created to provide public access to information about the committee’s work and to facilitate communication with the committee. The conclusions and recommendations of the committee’s reports thus far (see Box 1) are summarized in Appendix A.

For its evaluation of the questions concerning vaccines and autism, the committee held an open scientific meeting in February 2004 to hear presentations on issues germane to the topic (see Appendix B). Many of these presentations are available in electronic form (audio files and slides) on the project website. In addition, the committee reviewed an extensive collection of material, primarily from the published, peer-reviewed scientific and medical literature. The committee also commissioned a paper on autism and the immune system. A list of the



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