This chapter presents an overview of the combined cost-effectiveness/decision analysis approach taken by the committee. Although reasonably straightforward in principle, the necessary calculations* demand a substantial amount of quantitative information, expose areas of ignorance, and require value judgments as well as facts. The committee sought the best available data from published sources and experts as a foundation for its calculations. Although concerned about the probabilistic and subjective aspects of its estimates, the committee recognized these elements as unavoidable in a priority-setting exercise such as this one. When factual information was not available, the choice was whether needed probabilities should be made explicit or left implicit. The committee chose to identify and quantify pertinent probabilities rather than to leave them vague or unspecified.

The report strives to identify the sources and reasons for all assumptions and estimates. One purpose is to make it easier to adjust assumptions and assess their effects on the implied rank order. The explicit, quantitative approach also facilitates the performance of sensitivity analyses, in which selected estimates are varied systematically across their plausible ranges to examine their impact on the cost-effectiveness calculations.

Several assumptions underlie the analysis. Some of these are considered further in Chapter 8.

1. Only specified vaccines and diseases are assessed. The preliminary selection of candidates for new or improved vaccine development was based on expert views of the current state of knowledge about each disease pathogen and the corresponding host response. Appendix B summarizes the committee’s conclusions about some disease problems for which vaccine prospects are unclear or for which more basic research is required before targeted vaccine development will be realistic. If a candidate vaccine is omitted from the full analysis, it obviously will