The central analysis employs the probability of successful development indicated for each vaccine in Chapter 5. The effect of adopting a more optimistic but not unreasonable view was examined by assuming a 100 percent chance of successful development within the period set for likely time to licensure. The results are shown in Table 9.6. Such an assumption would not materially affect the choice of the top five vaccines.

As another sensitivity analysis, by way of example, we considered the effects of lowering the probability of successful development for a single, highly ranked, vaccine—RSV-ALV (Table 9.7). The original estimate reflected in Tables 9.1 and 9.2 was 80 percent. In order to eliminate RSV-ALV vaccine from the top five (based on expected health benefit: committee median perspective, Table 9.2), this probability would have to be less than 25 percent, in which case Herpesvirus varicellae vaccine (for normals and children) would surpass it.

Anticipated utilization rates used in the central analysis are those estimated by the method described in Chapter 6. These are for voluntary acceptance. They assume that new vaccines will not be used in combination with existing vaccines, and that use will reflect presently prevailing attitudes towards the diseases. Higher utilization rates probably could be achieved by combining vaccines or by instituting promotional/educational campaigns. To determine the effect of possible increased use on rankings, an optimistic utilization scenario was developed. In this scenario, it is assumed that the use rate for pediatric vaccines (including the attenuated live cytomegalovirus vaccine for adolescent females) is raised to 90 percent by vaccine combination or some other means. For adult vaccines (including the N. gonorrhoeae vaccine), the scenario assumes that the use rate is raised to 33 percent by promotional campaigns. If the estimated use rate is higher than the rate assumed in the optimistic scenario, the higher rate is used in the sensitivity analysis. Incremental vaccination program costs are recalculated for influenza vaccine (at 33 percent utilization) as described in Chapter 7.

The effects on the ranking of adopting this optimistic utilization scenario are shown in Table 9.8.

Assuming optimistic utilization rates would leave RSV, influenza, hepatitis B, and H. influenzae type b vaccines in the top five based on expected health benefit, and would move gonococcal vaccine into the top five as well, in place of varicella vaccine for high-risk persons. In addition, the subunit vaccine against influenza becomes much more cost-effective, being preferred to the ALV vaccine for willingness to pay value of greater than $33,000 per IME saved. Moreover, streptococcus group B vaccine replaces H. influenzae type b vaccine for willingness to pay values below $275,000 per IME. Herpesvirus varicellae vaccine (high-risk individuals) replaces hepatitis B vaccine for