trends could be examined, if desired, within the model proposed. These assumptions apply only to diseases under study and the current population projections: if other disease candidates are added to the list, the assumptions should be reexamined. Because of the trend in most developing countries toward greater relative numbers of individuals in the younger age groups, the major effect of adopting these assumptions would be to somewhat underestimate the benefits of vaccines reducing disease in these age groups, assuming incidence rates remain constant.
Because no vaccine in this analysis is predicted to have serious side effects, the current calculations omit adverse reactions, if desired, estimation of each vaccination program’s adverse effects can be incorporated into the benefit calculations. The predicted incidence of adverse reactions, the annual number of potential new vaccinees, and the IME values for the types of adverse conditions predicted can be used to calculate values representing the vaccine-induced morbidity and mortality (if any). These values for adverse effects may be used as a correction to PRMM figures. In the analysis of vaccine priorities for the United States, it was calculated that anticipated occurrence of adverse reactions necessitated only a very small adjustment of PRMM (i.e., less than 1 percent of PRMM).
For the reasons described above, adverse reaction values (and their costs) are not included in the tables and discussion that follow in this chapter. If other vaccine candidates are added to the analysis, however, their potential for adverse reactions should be evaluated.
The purpose of the accelerated vaccine development program is to expedite the realization of the benefits theoretically possible with various vaccines. It is appropriate, therefore, to account for the times at which benefits and costs associated with vaccine development and use would occur. Usually this is done by a process termed discounting (Weinstein and Stason, 1977), which can be applied both to the health benefits (of morbidity and mortality averted) and the costs incurred in vaccine development and use.
Factors affecting the predictions of the time to develop the vaccine candidates are discussed in Chapter 5. The predictions are related to probability of success and other issues discussed in that chapter and shown in Table 5.1.