infants is presented in other sections of the report. The committee notes here, however, that the analysis described in this report identifies many infectious agents whose disease burden could be prevented most effectively with a strategy of immunization of pregnant women, and it hopes that serious consideration will be given to addressing the significant impediment to all vaccine development brought on by liability concerns. The committee did not believe it was the appropriate group, however, to recommend a specific policy solution.
Models put a framework around previously incomparable data, and imperfect as the data can be, the committee nonetheless encourages the use of such evidence-based tools as aids, not mandates, for decisionmaking. If the results—the relative ranking of vaccine candidates—make intuitive sense (that is, if they conform to the informed judgment of the health care community) the model is probably correct. If the results are surprising (that is, a vaccine candidate ranks much higher or much lower relative to others than one would have predicted), a decisionmaker might ask if either the model or the data inputs are suspect. If not, then the model has been particularly useful. The experience in prioritizing reimbursement for health care interventions described in Chapter 6 is instructive. At times relative rankings run counter to the community’s beliefs, and thus, this model, like any model, should be viewed as malleable. There is always a role for informed judgment when deciding to what degree the results of a modeling tool drive policies, particularly when the limitations of the model have been made explicit. The 1985 IOM committee on vaccine priorities, in fact, included an acellular pertussis vaccine mostly because of the pivotal role that its development would play in increasing confidence in vaccine safety and ensuring a supply of vaccine. This was a qualitative consideration that the committee valued but that it could not enter directly into the model.
Ethical concerns are another such consideration. Health status measurements are discussed in detail in Chapters 4, 5, and 6. The committee used quality-adjusted life years (QALYs) in this exercise. The disability-adjusted life year is used by some researchers in these kinds of analyses, but for reasons explained in the chapters on methods (Chapter 4) and ethical considerations (Chapter 6), QALYs are a respectable and valid choice preferred by the committee. Although QALYs are a quantitative measure, they embody ethical considerations that cannot be directly quantified or weighted. The committee struggled with applying the health utility index in its QALY calculations, but in the end, it noticed remarkable inter- and intraperson consistency in the values obtained for similar health states. The committee expects and encourages continued research on this and other measures of health status.