Epidemiological and evolutionary consequences of targeted vaccination.

Recent theory has examined the way in which vaccination strategies are expected to influence the evolution of parasite virulence. Most of this work has assumed that vaccination is imposed on a homogeneous host population. However, host populations are typically composed of different types of individuals, with each type responding differently to infection. Moreover, actual interventions often focus treatment on those hosts that are likely to suffer the most ill effects of a particular disease. Here we consider the epidemiological and evolutionary consequences of interventions that focus vaccination on individuals expressing the greatest susceptibility to infection and/or the greatest vulnerability to mortality once infected. Our results indicate that predictions are very sensitive to the nature and degree of heterogeneity in susceptibility and vulnerability. They further suggest that accounting for realistic kinds of heterogeneity when contemplating targeted treatment plans and policies might provide a new tool in the design of more effective virulence management strategies.