  The success of a vaccination program is crucially dependent on its adoption
by a critical fraction of the population, as the resulting herd immunity
prevents future outbreaks of an epidemic. However, the effectiveness of a
campaign can engender its own undoing if individuals choose to not get
vaccinated in the belief that they are protected by herd immunity. Although
this may appear to be an optimal decision, based on a rational appraisal of
cost and benefits to the individual, it exposes the population to subsequent
outbreaks. We investigate if voluntary vaccination can emerge in a an
integrated model of an epidemic spreading on a social network of rational
agents that make informed decisions whether to be vaccinated. The information
available to each agent includes the prevalence of the disease in their local
network neighborhood and/or globally in the population, as well as the fraction
of their neighbors that are protected against the disease. Crucially, the
payoffs governing the decision of agents evolve with disease prevalence,
resulting in the co-evolution of vaccine uptake behavior with the spread of the
contagion. The collective behavior of the agents responding to local prevalence
can lead to a significant reduction in the final epidemic size, particularly
for less contagious diseases having low basic reproduction number $R_0$. Near
the epidemic threshold ($R_0\approx1$) the use of local prevalence information
can result in a dichotomous response in final vaccine coverage. The
implications of our results suggest the nature of information used by
individuals is a critical factor determining the success of public health
intervention schemes that involve mass vaccination.
