Speaker
Description
Virulence management, which studies the evolution of pathogen virulence (i.e., pathogen-induced mortality), shows that when vaccination reduces susceptible host density, selection may favor lower virulence. However, most studies assume fixed host behavior: a constant fraction of the population vaccinates throughout an epidemic. In reality, vaccination behavior is dynamic and shaped by social, epidemiological, and individual factors, producing temporal changes in vaccine uptake and altering the pathogen’s ecological environment and evolutionary trajectory. To investigate the effects of such behavioral dynamics on virulence evolution, we develop a system of ordinary differential equations describing epidemic dynamics with newborn vaccination. Virulence evolution follows a quantitative genetics–inspired framework, while vaccination decisions follow imitation dynamics reflecting social influence. We compare the model under different vaccination scenarios. Results show that behavioral feedbacks can generate recurrent outbreaks and evolutionary cycles of virulence, producing repeated mortality peaks. Strikingly, instantaneous death rates with vaccination dynamics can transiently exceed those without vaccination. Nevertheless, cumulative mortality remains lower with vaccination. Overall, our results highlight the interplay between epidemiology, evolution, and behavior in social-epidemiological systems. This highlights the need to include behavior in evolutionary epidemiology.
