Application of an economic model to the study of leprosy control costs.

The effectiveness of various control methods for reducing the incidence of leprosy have been tested over 20 years and compared with predictions made using the present current control method (early diagnosis and mass treatment). Specific vaccination of the whole population, a control measure yet to be developed, has been identified as the most effective strategy in the long run. A cost-effectiveness analysis has been carried out for three indicators, annual incidence, annual prevalence and cumulative prevalence at 20 years, using cumulative costs. The analysis indicates that specific vaccination at high levels of coverage is the most effective method for controlling incidence in the long term. Provided the cost of the vaccination campaign during the first years (roughly fourfold the funds required for carrying out the current strategy) can be supported, specific vaccination is also the most cost-effective method where a high level of effectiveness is required. Specific vaccination is still the most advantageous method if prevalence or cumulative prevalence are taken to indicate the effectiveness of leprosy control. The BCG-type of vaccination is not only less effective, it is also less cost-effective. Reducing the rate of abandonment of treatment (which in the model has been simulated by increasing the rate of resuming treatment) and earlier detection both appear as useful methods under conditions of severe budgetary constraints. Their ultimate effectiveness in terms of incidence reduction is, however, very small. As expected, segregation is costly and ineffective compared with other methods. In each simulation, the cost of treating the backlog of patients already ill or infected (incubating) at the time the control measures are initiated is high. Methods aimed at reducing transmission, such as vaccination, early treatment or segregation, have long-delayed effects on the cost even if incidence is reduced. The major cost item in these control measures is the prolonged or even life-long treatment of patients. The development of fast-acting, effective treatment is likely to be the only way to reduce the cost in the short term. Thus, in addition to research aimed at developing a vaccine for leprosy, resources should also be allocated for developing new therapeutics.