BCG vaccination (prevention) and Case-finding followed by treatment (cure) are two universally accepted methods for controlling tuberculosis. BCG trials in selected populations have provided some information on the protective value of BCG, generally over short periods of time (below 20 years) and mainly among younger populations. Efficacy of different drug regimens for treatment of tuberculosis are well established and a number of studies on the effectiveness of different types of treatment programmes on the patient population are available. However, the manner in which BCG and treatment affect the four epidemiological indices of prevalence & incidence of infection and prevalence & incidence of disease in the community, over a period of time, has not been reported in detail.

This paper describes a simple set of models which can be used to predict the trend from these indices under different types of TB programmes (including no programme) which can be depicted as a combination of 5 programme parameters. How these models can be used for planning and assessment of programmes have been demonstrated by some examples. The trend in the incidence of disease obtained from this model is similar to that reported by Waaler et al in 1974. Unlike earlier models, the present model starts with cases and the calculations involved are simple enough to be handled by calculators and computer facilities are not necessary.