Contagion exposure and protection technology

Individuals adopt diverse measures to prevent contagion during interactions. I propose a model to study the implications of the protection technology on the prevalence of infections and on welfare at different levels of exposure. I find that the effect of aggregate exposure on prevalence and on protection inefficiencies depends crucially on the characteristics of the available protection technology. For example, a vaccine may yield lower infection rates and smaller costs of decentralization as exposure increases, but only if the protection it provides is sufficiently long lasting. Other protection technologies, such as those used for cybersecurity, may lead to coordination failures. The analysis has implications for disease eradication, the desirability of interventions with and without universal vaccines, and coordination failures in cybersecurity.