Optimal Vaccination Strategies for an Heterogeneous SIS Model

Abstract

We study in a general mathematical framework the optimal allocation of vaccine in an heterogeneous population. We cast the problem of optimal vaccination as a bi-objective minimization problem min(C($\eta$),L($\eta$)), where C and L stand respectively for the cost and the loss incurred when following the vaccination strategy $\eta$, where the function $\eta$(x) represents the proportion of non-vaccinated among individuals of feature x.To measure the loss, we consider either the effective reproduction number, a classical quantity appearing in many models in epidemiology, or the overall proportion of infected individuals after vaccination in the maximal equilibrium, also called the endemic state. We only make few assumptions on the cost C($\eta$), which cover in particular the uniform cost, that is, the total number of vaccinated people.The analysis of the bi-objective problem is carried in a general framework, and we check that it is well posed for the SIS model and has Pareto optima, which can be interpreted as the ``best'' vaccination strategies. We provide properties of the corresponding Pareto frontier given by the outcomes (C($\eta$), L($\eta$)) of Pareto optimal strategies.