was estimated to be very high, and the interval from vaccination to realization of health benefits is very short. In the absence of experience with therapeutic vaccine strategies, it is not clear that the results obtained were predictable at the outset of this analysis. The committee hopes that the results will encourage continued research into the use and benefits of this relatively new class of vaccine strategies.

As mentioned, the results presented above are based on the full analysis described at the beginning of the chapter. Readers might question the effects of changing certain assumptions or components of the model, and the committee tested the effects of changing certain assumptions. To illustrate how the model could be used by vaccine program planners, the committee assumed that the vaccines are currently available (i.e., requiring no more time or costs for development). There was no change in the assignment of vaccines to Levels I-IV. When the committee further assumed that the vaccines are currently available, 100% effective, and utilized by 100% of the target population (i.e., the ideal scenario; an analysis requested of the committee by the project sponsor, NIH), five vaccines shifted into an adjacent category. Specifically, four vaccines in Level II—chlamydia, melanoma (therapeutic), mycobacterium tuberculosis, and respiratory syncytial virus—moved into Level I. A fifth vaccine, against Coccidioides immitis, moved from Level IV to Level III.

Licensure of the Level I candidate vaccines poses several challenges for vaccination programs and health care providers. For example, the committee believes that a CMV vaccine would best be administered during puberty to protect neonates from CMV infection. This would require acceptance by parents, children, and health care providers that the potential for sexual activity among young adolescents argues for ensuring that the vaccine is administered to 12-year-olds (the proxy age used in the modeling). This also will require a health care milieu that is more capable than it is now of routine vaccination at ages other than infancy. Factors such as health beliefs, health care practices, performance measurements for health plans, and school entry laws have contributed to relatively successful childhood immunization efforts. Similar incentives are not yet as widespread for the newly emerging “adolescent” or “pubertal” vaccination visits that are now recognized as being important for protection against measles and rubella, for example.

Another challenge will be immunization of pregnant women against Group B streptococcus. Previous chapters discussed the barriers, particularly the legal barriers, to the development of vaccines to be administered during pregnancy. The committee’s analysis assumes that these barriers have been overcome. The analysis also assumes that immunization of pregnant women can become a standard part of prenatal care. With an alternative assumption that few pregnant