Interventions to mitigate post-infection morbidity: Management insights from simple models

A variety of pathogens that cause acute disease can also affect their host long after recovery. These post-infection effects lead to elevated costs for individuals and societies, which can be mitigated by large-scale interventions. Here, we examine the management of post-infection morbidity with mathematical models. First, we show that long-term usage of nonpharmaceutical interventions can reduce post-acute burden. Second, to investigate how post-infection effects affect optimal vaccination coverage, we generalize and expand on classic epidemiological-economic models. We include post-infection costs, and consider the cost of vaccination as a general increasing function of coverage. If there is some sub-elimination coverage that locally minimizes costs (beyond elimination), we show that the decision of whether to vaccinate or not is independent of the transmission rate (however elimination does depend on this). Echoing existing theoretical results with exponentially increasing costs, we find that if vaccination costs either only accelerate or only decelerate with increased coverage, there is a unique, transmission-independent interior level of vaccination coverage (nonzero and sub-elimination) that locally minimizes or maximizes societal costs, respectively. In all settings, we show that post-infection effects can substantially shift societal incentives toward elimination. Furthermore, when costs of vaccination change concavity, the optimal coverage level is very sensitive to post-infection costs: a small increase can shift optimal coverage from none (or low coverage) to elimination. Our findings demonstrate that post-infection morbidity has important implications for policy and management, and that there is an urgent need to quantify costs of post-infection effects and of large-scale vaccine deployment.