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Vaccine Characteristics

The vaccine characteristics used in this comparison are described in Chapter 5, Tables 5.1. and 5.2. Detailed information on specific vaccines is included in Appendixes D-1 through D-19.

Target Population

Target populations for the vaccines are described in the relevant appendixes and briefly outlined in Table 7.1. The number of new potential vaccine recipients entering the target population each year must be determined to calculate the vaccine costs for each immunization program. These calculations are based on the envisaged target population and the 1984 population projections (see Chapter 4). The basis for the calculation of the number of new potential recipients of each vaccine is shown in Table 7.1 and described more fully in relevant appendixes.

In addition to indigenous populations at risk from the various diseases in developing countries discussed here, it is likely that travelers and personnel from developed countries who are stationed overseas would also be given some vaccines. Relative to the indigenous target populations, the number of such potential vaccinees is judged to be insignificant. However, decision makers may wish to consider the size of these groups and the benefits that would result from their protection when making ultimate choices on vaccine priorities.

Vaccine Preventable Illness

For each disease, an estimate of the potential vaccine preventable illness is needed. This can be expressed either as a proportion of the total burden of illness, or developed as estimates of the numbers of cases, complications, sequelae, and deaths that result from each disease. These estimates are derived from the distribution of the disease burden; the envisaged target population; the characteristics of the vaccine (e.g., the number of doses necessary to achieve full protection) and the likely age(s) for vaccine delivery; and for some diseases, where appropriate, the proportion of the disease affecting an identified high-risk group or target population.

In this analysis, VPI was expressed as a proportion of the total disease burden. The factors used for each vaccine/disease combination to estimate VPI are discussed in Appendixes D-1 through D-19.

Trends in Disease Burden and Population Numbers

Calculations of morbidity, mortality, and costs assume that the effects of trends in disease burden and population size (between 1984 and the achievement of steady-state benefits) would not be of sufficient magnitude to obscure differences between diseases. The effects of such

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