In this paper the role of acquired immunity in disease control is examined with particular emphasis on vaccination against B. bovis. A method is then developed to predict the change in disease incidence that will follow the introduction of a vaccination program. This method involves the extension of the disease prediction model developed in the previous paper to include vaccination. The extended model is then used to estimate the number of cases of disease prevented by vaccination for each age and sex class and each year of the vaccination program. The method is then applied to determine the number of cases of disease prevented by vaccination against B. bovis. The information produced is used as an input to determine the production loss avoided due to vaccination against B. bovis in a subsequent discussion paper. This paper examines the role of acquired immunity in disease control then outlines the development of a model to predict the effect of vaccination programs on the number of cases of disease. The model is an expanded version of the disease prediction model developed in the previous discussion paper.