Emergence of shield immunity during spatial contagions

Abstract

Abstract Contagions spreading across space—including epidemics, infodemics, and socio-economic turbulence — generate complex geo-spatial patterns shaped by contagion state and risk-driven population mobility. Distribution of resources for mitigating these contagions adds further complexity. We present a concise, generic framework to model various contagion types within a space characterized by bounded risk disposition parameters and generalized resource effectiveness. Specifically, we explore how (i) risk-averse behavior of “inoculated” individuals and (ii) resource effectiveness in reducing contagion “incidence” influence pattern formation and spread of infection, opinion polarization, social myths, and socio-economic disruptions. We show that “inoculated” individuals interacting with affected populations may help minimize contagion impact by curbing further transmission. We identify this as a generalized form of shield immunity and explain its emergence in terms of individual risk disposition. This shielding effect is strongest in socio-economic turbulence, moderate in epidemics, limited in social myth spreading, and not observed in polarization dynamics.