title: Self-enforcing regional vaccination agreements.
abstract: In a highly interconnected world, immunizing infections are a transboundary problem, and their control and elimination require international cooperation and coordination. In the absence of a global or regional body that can impose a universal vaccination strategy, each individual country sets its own strategy. Mobility of populations across borders can promote free-riding, because a country can benefit from the vaccination efforts of its neighbours, which can result in vaccination coverage lower than the global optimum. Here we explore whether voluntary coalitions that reward countries that join by cooperatively increasing vaccination coverage can solve this problem. We use dynamic epidemiological models embedded in a game-theoretic framework in order to identify conditions in which coalitions are self-enforcing and therefore stable, and thus successful at promoting a cooperative vaccination strategy. We find that countries can achieve significantly greater vaccination coverage at a lower cost by forming coalitions than when acting independently, provided a coalition has the tools to deter free-riding. Furthermore, when economically or epidemiologically asymmetric countries form coalitions, realized coverage is regionally more consistent than in the absence of coalitions.
authors.affiliation: Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK pklepac@alum.mit.edu.
authors.forename: Petra
authors.initials: P
authors.lastname: Klepac
authors.affiliation: Center for Disease Dynamics, Economics and Policy, Washington, DC 20036, USA.
authors.forename: Itamar
authors.identifier: http://orcid.org/0000-0001-8391-6660
authors.initials: I
authors.lastname: Megiddo
authors.affiliation: Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA Woodrow Wilson School of Public and International Affairs, Princeton University, Princeton, NJ 08544, USA Fogarty International Center, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Grenfell
authors.affiliation: Center for Disease Dynamics, Economics and Policy, Washington, DC 20036, USA Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA Public Health Foundation of India, New Delhi 110070, India.
authors.forename: Ramanan
authors.initials: R
authors.lastname: Laxminarayan
mesh_terms: D000818:Animals; D006801:Humans; D018448:Models, Immunological; D014611:Vaccination
keywords: SIR model; epidemic dynamics; metapopulation; regional cooperation; transboundary movement