It was assumed that preventive vaccines would achieve an efficacy level of 75%. The efficacy of therapeutic vaccines was assumed to be 40%. A utilization rate of 10%, 30%, 50%, 60%, or 90% was assigned to each vaccine.

For each condition, cost-effectiveness ratios were calculated at three stages in the analysis. The first ratio examines the potential impact of the vaccine on morbidity and costs under the assumption that the vaccines are available immediately without any additional cost or time for development and that they are fully efficacious and are used by the entire target population. This comparison focuses attention on what might be considered an ideal vaccine benefit. The second cost-effectiveness ratio factors in the adjustments for incomplete efficacy and use, which tend to increase the cost of achieving the anticipated health benefit. The final ratio, which corresponds to Equation 2, shows the impact of the time and money needed to develop these vaccines. Some vaccines that promise substantial benefit require longer and more expensive periods of development, whereas others that offer smaller benefits are expected to be available more quickly and cheaply. In general, the committee found that the adjustments for efficacy and utilization had a more substantial impact on a vaccine’s cost-effectiveness than the additional time and cost needed for development.