Optimal Vaccination Strategies and Rational Behaviour in Seasonal Epidemics

TL;DR

This paper analyzes vaccination strategies in a seasonal SIR epidemic model, deriving optimal and Nash equilibrium vaccination policies, with explicit formulas under certain transmission conditions, highlighting differences between mandatory and voluntary vaccination approaches.

Contribution

It introduces a framework for deriving both optimal and Nash vaccination strategies in a seasonal SIR model, including explicit solutions for specific transmission rates.

Findings

Existence of both optimal and Nash vaccination strategies proven.

Explicit formulas provided for specific transmission rate forms.

Strategies may be Radon measures, not just functions.

Abstract

We consider a SIR model with temporary immunity and time dependent transmission rate. We assume time dependent vaccination which confers the same immunity as natural infection. We study two types of vaccination strategies: i) optimal vaccination, in the sense that it minimizes the effort of vaccination in the set of vaccination strategies for which, for any sufficiently small perturbation of the disease free state, the number of infectious individuals is monotonically decreasing; ii) Nash-equilibria strategies where all individuals simultaneously minimize the joint risk of vaccination versus the risk of the disease. The former case corresponds to an optimal solution for mandatory vaccinations, while the second correspond to the equilibrium to be expected if vaccination is fully voluntary. We are able to show the existence of both an optimal and Nash strategies in a general setting. In general, these strategies will not be functions but Radon measures. For specific forms of the transmission rate, we provide explicit formulas for the optimal and the Nash vaccination strategies.