Xue Feng, Princeton University

Abstract

Voluntary vaccination coexists with mandatory vaccination on a global and even national scale. For example, most states in the US use voluntary vaccination for MMR (a combined vaccine against Measles, Mumps and Rubella); but in Mississippi, West Virginia and California, MMR is a mandatory requirement for school entry and only medical exemptions of MMR are allowed. This project tries to compare these two strategies from the perspective of epidemiology and economic cost. Specifically, with voluntary vaccination, individual decisionmaking depends on the perceived payoffs of disease and vaccines rather than the real ones. Population structure on which information and diseases spread and the ability of processing information are two factors leading to the difference between perceived and real payoffs. Here, network and prospect theory are used to capture features of these two factors, respectively. For well-mixed populations, the voluntary strategy gives rise to an endemic, non-vaccinator equilibrium, and the mandatory strategy takes more time to reach the stable state with endemic disease and high vaccination coverage. Even though the voluntary strategy costs less than the mandatory one when populations stabilize, the former leads to much more cumulative cost during the evolutionary process. In addition, people can move easily and freely, and regions with these two opposite strategies are not isolated. The coupling of these two strategies by migration of people in both well-mixed and structured populations is an ongoing study.