The costs of future research and clinical trials that would be needed to complete development of a vaccine and have it licensed, designated C_D, are a mix of public- and private-sector expenditures. They were assumed to fall at one of six levels: $120 million, $240 million, $300 million, $360 million, $390 million, or $400 million. A development cost was assigned to each vaccine on the basis of the committee’s assessment of the current stage of the vaccine’s development. In terms of the analysis, the cost of vaccine development is treated as an amortized fixed cost. The committee also 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 the times when the associated costs and benefits of the vaccines will be realized.

The cost of vaccine use is a function of the cost per dose of the vaccine, the cost to administer the vaccine, the number of doses each person must receive to be fully immunized, and the size of the population targeted to receive the vaccine:

where C_I is the annual cost of immunizing the target population, d is the cost per dose of the vaccine, a is the cost of administering a dose of vaccine, Dose is the number of doses each person must receive, and Pop is the size of the target population.

A vaccine’s cost per dose is represented by the purchase price rather than the marginal cost to manufacturers of producing a single dose. The cost of prophylactic vaccines was assumed to be either $50 or $100. The cost of therapeutic vaccines was set at $500. The marginal cost of administering a dose of vaccine was set at $10. For most vaccines, it was assumed that three doses would be needed to achieve full immunization. In specific cases (e.g., influenza vaccine), the number of doses required was altered to match the available evidence.

The committee defined a target population for each vaccine considered, and the size of that target population was determined by using current estimates of the U.S. population by age. For vaccines intended for use in infants or adolescents, the target population was assumed to equal the birth cohort or the population at age 12, respectively. For vaccines intended for use in special subpopulations (e.g., travelers, residents in a specific geographic region, persons with chronic illness) the basis for the estimate of the size of the target population is described in detail in the Appendixes.

It was assumed that 5 years would be required following licensing to achieve stable, maximum levels of use of preventive vaccines. For therapeutic