tions included in the analysis, the completeness of reporting varies by condition. Some estimates are based on data from state- or community-level studies. Others rest largely on expert judgment. The specific sources of data for each condition are described in the Appendixes. For all conditions, the analysis uses incidence data, that is, the number (or rate) of new cases that would be expected during 1 year. For chronic illnesses such as multiple sclerosis, these data will differ from the estimates of prevalence that are often reported.

As described in a previous section, discounting is applied to future health benefits as well as costs. The timing of the health benefits expected from the use of the potential new vaccines included in the committee’s analysis will vary depending on the intervals between the typical age at immunization and the age at onset of an illness or the age at death. The intervals calculated for the analysis are the following: the time from vaccination to the average age at onset of illness, and the difference between the average age at onset of illness and average age at the time of illness-related death. The latter is of interest for those acute conditions for which the age at death from the condition differs markedly from the overall age of patients with that condition. The time interval related to premature death following a period of chronic illness is accounted for separately.

Age at vaccination was determined by the vaccination strategy, as reflected by the target population. Most cases fall into one of the following categories:

See Table 4–1 for information on the designated target population for each candidate vaccine.

To calculate health benefits anticipated with vaccine use, the QALYs associated with each health state were combined. First, the state-specific QALYs were summed for each morbidity scenario. By using the scenario totals, the QALYs lived with the condition under study were subtracted from the QALYs for the general population without the condition. This provides an estimate of the QALYs that could be gained in each scenario with vaccine use.