One of the conceptually important uses of epidemiological models is to provide some basic guidelines for public health practitioners. Models have two primary uses in applied settings. First, as we have seen in previous chapters, statistical data analyses and model fitting permit basic epidemiological characteristics of pathogens to be uncovered. This, in conjunction with empirical observations, enables epidemiologists to develop a picture of the kind of pathogen they are faced with, such as its transmission potential, routes of transmission, and latent and infectious periods. The second use of epidemiological models is to provide a means of comparing the effectiveness of different potential management strategies.
The most straightforward objective is simply to minimize transmission within a population, with the ultimate aim of reducing it to zero. Alternatively, we may wish to minimize the occurrence of disease (or severe illness). Although for many infectious diseases these two objectives may amount to the same control outcomes, for others this change in emphasis can have dramatic implications for control strategies. For example, infectious diseases such a rubella or toxoplasmosis are associated with minimal health risks when affecting the young or the old, whereas infection in pregnant women can have very serious consequences. In reality, a range of constraints and trade-offs may substantially influence the choice of practical control strategy, and therefore their inclusion in any modeling analysis may be important. These limitations may be simply logistical, in terms of the number of units of vaccine that can be administered in a given time frame, or epidemiological such as adverse reactions to a vaccine. 

In this chapter, we review some mathematical models of different types of control strategies available to decision makers, with some of their inherent limitations and the general principles that emerge from their analyses. We start by considering alternative aspects of vaccination, before discussing control of smallpox by a combination of vaccination and contact reduction.