The scenario-specific QALYs to be gained were multiplied by the proportion of cases of illness experiencing that scenario and were summed across all scenarios. This total was multiplied by the number of cases, or by the number of deaths for the QALYs associated with mortality, to calculate the overall benefit that the use of a vaccine for the condition under study would be expected to have in the population. If subpopulations were used in the analysis, the results were calculated for each subpopulation, and the subpopulation results were summed to produce an estimate of the total health benefit.

Costs associated with the development and use of a vaccine provide the numerator of the cost-effectiveness ratio for each of the cases considered by the committee. The cost components include the costs of vaccine development, the cost of vaccine use, and the reduction in health care and related costs that would be expected with vaccine use. All cost estimates are presented in constant dollars.

The costs of future research and clinical trials needed to complete development of a vaccine and have it licensed are a mix of public- and private-sector expenditures, of which the private-sector component is especially difficult to estimate. In the absence of real data regarding these development costs, they were assumed to fall at one of six levels: $120 million, $240 million, $300 million, $360 million, $390 million, or $400 million. The committee assigned each candidate vaccine to one of these cost levels on the basis of its assessment of the current stage of the vaccine’s development (see Table 4–1). For many conditions under study, work is being done on more than one type of candidate vaccine. The committee did not think that differences among the candidate vaccines in terms of development costs (or cost per dose or effectiveness) were likely to be significant enough to warrant separate analysis.

The committee also considered the time required to achieve licensure of a vaccine. Since specific evidence on which to base fine distinctions among the candidate vaccines was not available, the committee assigned each candidate vaccine to one of three development intervals: 3, 7, or 15 years. Discounting incorporated this development interval to adjust for the differences in when the associated costs and benefits of the vaccines will be realized.