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Table 8.2 provides a summary of the current prevention, control, and treatment measures for diseases in this analysis. More complete information on many of these diseases is presented in Warren and Mahmoud (1984) and in a series of monographs on selective primary health care that will be published shortly by Walsh and Warren (in press).

Some caution is warranted in assuming that vaccine development is less urgent if alternative prevention, treatment, or control measures are available. The history of vector control (with pesticides) and drug therapy for a wide range of diseases indicates that even with continued efforts, these measures may become less effective (or completely ineffective) because of increasing vector or pathogen resistance.

For example, certain strains of Mycobacterium leprae recently have become resistant to dapsone, the principal drug used to treat leprosy for the past 20 years. The prevalence of drug resistance has increased in some areas from 1 to 2 cases per thousand in 1966 to as high as 100 per thousand in 1981 (Bloom, personal communication, 1985). Resistance to dapsone, compounded by the considerable expense of rifampicin and the generally unacceptable side effects (skin coloration) of clofazimine, necessitates the pursuit of preventive immunization strategies.

It was not within the charge of this committee to address the relative merits of immunization versus other means of controlling diseases. It should be noted, however, that immunization generally has been shown to be one of the most cost-effective measures for improving health and that it is relatively free of the resistance problems afflicting vector control and drug therapy. Papers by Feachem and colleagues demonstrate the use of cost-effectiveness analysis in comparing alternative approaches to combatting particular diseases (Ashworth and Feachem, 1985; de Zoysa and Feachem, in press; Feachem, 1983, 1984; Feachem and Koblinsky, 1983, 1984; Feachem et al., 1983).

For rabies, immunization of the major vector, domesticated or semi-domesticated dogs, could be part of an overall strategy of disease prevention. Although cheaper human-use vaccines with fewer side effects would provide considerable benefit, developing animal vaccines that are inexpensive and easily administered (e.g., through baits) may offer the major hope for reducing the incidence of rabies in many countries. This analysis addresses only the potential benefits of vaccines for human use.

Epidemiologic and Clinical Features

The proposed system for calculating a vaccine’s potential health benefits uses average annual incidence rates to develop disease burden estimates. This process might understate the importance of certain diseases that occur in epidemic form and produce severe clinical symptoms. A large epidemic of such a disease could overwhelm health care services in developing countries. Because of limited resources, these countries are often barely able to provide appropriate care under normal circumstances. The potential for widespread epidemics also might exacerbate public anxiety about such diseases. Table 8.3 summarizes

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