Human behaviour, cost-effectiveness analysis and research and development priorities: the case of a schistosomiasis vaccine.

Cost-effectiveness analysis has been widely used in the health sector to guide decisions about where scarce resources aimed at disease prevention or control should be invested. It has rarely been used to guide decisions about what type of health research should be funded. In addition, the validity of the behavioural assumptions underlying the economic analysis is rarely considered explicitly. This paper explores the use of cost-effectiveness analysis to set priorities for research using the development of a schistosomiasis vaccine as an example. It then explicitly considers behavioural factors which might affect the accuracy of the calculations. A 'product profile' for the new technology is derived which can be used by developers as a target to aim at. To ensure that the vaccine would be more cost-effective than the currently preferred option for the control of schistosomiasis, chemotherapy based on praziquantel, researchers need a vaccine which has sufficient duration of protection to be delivered as part of the regular childhood immunization programme me. The cost of adding it to existing vaccination schedules should not be more than US$4.30 per child in excess of the cost of one round of chemotherapy. It should, ideally, have an efficacy over 80%. These results, however, depend on a number of cultural and behavioural factors which are often ignored in cost-effectiveness studies. For example, low rates of school attendance would increase the cost of contacting children for a chemotherapy programme and increase the relative attractiveness of a vaccine. For chemotherapy to be effective, children also need to comply each year for a number of years. Falling rates of compliance over time would reduce the effectiveness of chemotherapy and increase the attractiveness of a vaccine. But on the other hand, even though a vaccine may still be more cost-effective than chemotherapy at relatively low levels of vaccine efficacy, if mothers perceived the vaccine to be ineffective and refused to bring their children for vaccination, the success of the entire childhood immunization programme could be threatened.