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women will be immunized, the development of a Group B streptococcus vaccine becomes much less favorable (see Level III).

A third challenge will be acceptance of vaccines using DNA-based technologies. The committee has not factored into the analysis the effect that fear or reluctance might have on the extent to which this emerging technology might be used. The final challenge relates to therapeutic vaccines. Their effectiveness will depend on the early detection of an incipient disease; the committee has not envisioned how this might be done, especially for the therapeutic vaccine for insulin-dependent diabetes mellitus (IDDM). The committee assumes that, during the 15 years of development that remain until the expected licensure of these candidate vaccines, clinical research will provide a better understanding of the population at risk of IDDM and a means of screening for early signs of pancreatic ϑ-cell destruction.

The Level II candidate vaccines include many of the candidate vaccines from the 1985 IOM report on vaccine priorities. This set includes candidate vaccines for sexually transmitted diseases, important pediatric viral infections, bacterial and viral infections associated with long-term chronic disease states, and a therapeutic vaccine directed against a cancer, melanoma. The challenges posed by the licensure of these candidate vaccines are similar to those discussed above for the most favorable set. Vaccines to be administered during puberty require health care delivery systems and practices not yet adequately developed.

The placement in Level II of a vaccine directed against tuberculosis illustrates an interesting point. Although tuberculosis is a very serious disease with high associated health care costs, the number of new cases of tuberculosis is much lower than the number of new cases of many of the other diseases considered in the committee’s analysis. However, the assumption by the committee that the vaccine would be given to high-risk populations in a very targeted manner means that program costs are low compared with the cost of annual immunization of the birth cohort of almost 4 million infants.

The Level III candidate vaccines include vaccines to be given during puberty (or during pregnancy, but with a low utilization rate) to protect newborns and infants and vaccines to be administered during infancy to prevent diseases in infants and all others. Challenges related to immunization of pregnant women and of adolescents were discussed above. The committee has assumed that utilization of all vaccines during puberty will be in a midrange of approximately 50%. A Group B streptococcus vaccination strategy that targets girls during puberty or pregnant women with an assumption of a 10% utilization rate falls into Level III. An assumption of a high rate of utilization during pregnancy moves the Group B streptococcus vaccination strategy into the cost-saving set (Level I) of candidate vaccines, as discussed above.

The committee began its deliberations before the licensure of a rotavirus vaccine in 1998. The committee finalized its analysis of rotavirus vaccine with two separate assumptions. One analysis assumed that licensure was imminent in 3 years and required development costs. The other analysis assumed that licen-

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