Vaccination programmes for rare infectious diseases

A community of fixed size is exposed to the risk of a minor outbreak of a fatal infectious disease. Given that there exists a risk of dying from the vaccination, the proportion of individuals to be vaccinated against the disease, such that the mean number of deaths is a minimum is determined. The approach is illustrated with reference to the smallpox vaccination programme of the U.S.A. The method may also be applied when it is desired to minimize mean costs due to nonfatal infectious diseases.