unclear or for which more basic research is required before targeted vaccine development will be realistic (see Appendix I). If a candidate vaccine is omitted from the full analysis, it obviously will not appear in the rank order, and no conclusions should be drawn regarding its position relative to the assessed contenders.

Differences between the assessments of vaccine candidates for diseases of importance in the United States (Institute of Medicine, 1985) and in the developing world (this volume) mean that values for (or relative rankings based on) benefits and costs should not be compared between analyses. In the first exercise an effort was made to calculate absolute likely benefits that would accrue from vaccine development and the actual net costs (including costs of treatment averted) associated with their use. Because real values were calculated, the incremental cost per unit of benefits could legitimately be used to differentiate between vaccine candidates in the interpretation of rankings on these criteria.

In the present analysis, the committee treated certain factors affecting actual vaccine benefits and net costs differently than in the first report. Vaccine utilization is not incorporated into the calculation of benefits (for reasons discussed in Chapter 6), hence benefits are potential rather than expected. Utilization is also not included in cost calculations, and disease treatment costs are also not included (see Chapter 4).

These differences in methods have important consequences. The values derived for the health benefits and the expenditures on vaccines to achieve them should be viewed as representing relative vaccine attributes and not their absolute magnitude. Thus, as noted above, it is not appropriate to compare health benefit or cost calculations between the assessments presented in this volume and its companion (Institute of Medicine, 1985).

The committee’s method can produce a priority ranking of candidate vaccines, but it is silent on the question of how many of the vaccines are worthy of development. The committee expressly refrained from equating dollars with the value of any health benefits.

The analysis has no bearing on basic scientific research. it does not compare the value of further investment in basic scientific research with the benefits or costs of vaccine development.