reconsideration at this time of the current childhood immunization schedule or of any specific vaccine.

Research

The committee concluded that the findings available from epidemiological sources and consideration of possible biological mechanisms—which were deemed weak—do not at this time warrant specialized studies of possible associations between multiple immunizations and immune system dysfunction. Instead, the committee encourages epidemiological studies 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.

Epidemiological Studies

The committee emphasizes the need for continuing surveillance of vaccine recipients and possible adverse events. Changes in the immunization schedule may present opportunities to study whether or not the incidence of adverse health outcomes also changes. However, one of the challenges in addressing concerns about multiple immunizations is identification of appropriate and adequately sized study populations; allergy or autoimmune diseases have complex risk factors and potentially long intervals between vaccine exposure and diagnosis.

Several vaccine-related data resources already exist, including the Vaccine Adverse Event Reporting System (VAERS), the Vaccine Safety Datalink (VSD), and state and local immunization registries. 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 study type 1 diabetes and other important autoimmune diseases.

In addition, surveillance of autoimmune diseases and allergic disorders should be strengthened. Despite the routine diagnosis of asthma, finding a widely accepted definition for the disease has been problematic (Samet 1987, Toelle et al., 1997). The absence of a universally accepted definition of asthma makes it difficult to determine a consistent operational definition for epidemiological studies (IOM, 2000).

Disease registries and long-term research programs that identify individuals with these diseases, or with known genetic risk factors, could be an efficient means of finding subjects for either retrospective or prospective studies of possible vaccine-related risks. The committee recommends exploring the use of such 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



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