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comparing the anticipated health benefits and costs of vaccine use across drastically different forms of illness, ranging from pneumonia, ulcers, and cancers to temporary and long-term neurologic impairments. Furthermore, some of the vaccines included in the study are intended to treat illness, while most will be used in the more familiar role of preventing disease.

Cost-effectiveness analysis was judged to be the most satisfactory way to make these comparisons. The basis of comparison typically is a cost-effectiveness ratio that is expressed as cost per unit of health benefit gained. Monetary costs—the numerator of the ratio—reflect changes in the cost of health care that are expected to result from the use of an intervention such as a new vaccine plus costs associated with developing and delivering the intervention. Health benefits—the denominator of the ratio—increasingly are measured in terms of quality-adjusted life years (QALYs) gained by using the intervention under study. QALYs are a measure of health outcome that assigns to each period of time a weight, ranging from 0 to 1, corresponding to the health-related quality of life during that period, where a weight of 1 corresponds to optimal health, and a weight of 0 corresponds to a health state judged equivalent to death; these are then aggregated across time periods (Gold et al., 1996). The concept of QALYs, developed in the 1970s, was designed as a method that could integrate the health improvements for an individual from changes in both the quality and quantity of life, and could also aggregate these improvements across individuals (Torrance and Feeny, 1989). QALYs provide a summary measure of changes in morbidity and mortality that can be applied to very different health conditions and interventions. Interventions that produce both a health benefit and cost savings are inherently cost-effective, but many other interventions that do not save costs produce benefits at costs that are judged to be reasonable.

Although cost-effectiveness analysis facilitates comparisons among interventions, comparisons across studies are often undermined by critical differences in assumptions and analytic techniques. A report by the Panel on Cost-Effectiveness in Health and Medicine (Gold et al., 1996), convened by the U.S. Public Health Service, reviews the field and provides recommendations intended to improve the quality and comparability of studies. In its assessment of potential new vaccines, the committee has generally followed the recommendations of that panel. An analysis such as the one performed by the present committee is a valuable tool in a variety of contexts for decisionmakers who must set priorities and allocate resources. It simplifies a complicated picture in which vastly different forms of illness and health benefit must be compared and related to a variety of costs. It cannot, however, address all of the qualitative judgments that shape policy decisions. The analysis cannot provide the value judgments required to determine whether expected health benefits and costs justify a particular investment in vaccine development. The aim of the analysis is to clarify trade-offs in decisions to invest in the development of one vaccine as compared to another.

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