aversion to chronic or acute morbidity than the median set and a constructed age-neutral profile (i.e., for each morbidity category, calculate the geometric mean of median IME values across different age groups). The results of the ranking process with these profiles would then identify the extent to which differences of opinion regarding chronic or acute morbidity could alter rankings. (For a range of 14 important diseases in the United States, adopting a hypothetical age-neutral IME perspective, rather than the committee median that disfavored death and morbidity most in the 15–24 years age group, did not significantly alter the ultimate rankings [Institute of Medicine, 1985]).

Other sensitivity studies around the central analysis are also possible. These include the effect on the rankings of various predictions about the number of vaccine doses needed (which would affect expenditures on vaccines) or various predictions about individual vaccines (e.g., the probability of successful development of a vaccine).

The impact on rankings of using alternative assumptions for choosing the target population for some vaccines could also be tested, it would entail, however, more extensive recalculations, including reestimation of the disease proportion that is vaccine preventable.

The committee believes that a major strength of this analysis is that it encourages those using it to examine all judgments and assumptions about the selected vaccine preventable diseases. The committee recommends use of the proposed system by government decision makers. New candidates should be assessed as they become technically feasible and new data should be incorporated as they become available.

Data for disease comparisons are lacking in some areas and are of variable reliability in others. Further, data on the pathogen serotypes prevalent in particular regions may also be lacking.

Better data bases in these areas would facilitate making rational choices on vaccine development priorities and vaccine formulation. Therefore, NIAID and other national and international organizations should consider means to improve available epidemiological data on infectious diseases.

Institute of Medicine. 1985. New Vaccine Development: Establishing Priorities, Volume I. Diseases of Importance in the United States. Washington, D.C.: National Academy Press.