Vaccination Dilemma in the thermodynamic limit

TL;DR

This paper models the vaccination decision-making process in large populations using an analytical approach based on the 1D Ising model, revealing insights into age-dependent vaccination behaviors and informing public health strategies.

Contribution

It introduces a novel application of Nash equilibrium mapping from the 1D Ising model to analyze vaccination choices in the thermodynamic limit, comparing it with other models.

Findings

Nash equilibrium mapping aligns well with agent-based simulations.

Darwinian evolution model diverges from other models in predicting behavior.

Older populations are predicted to have near 100% vaccine coverage, younger populations less so.

Abstract

The vaccination game is a social dilemma that refers to the conundrum individuals face (to get immunized or not) when the population is exposed to an infectious disease. The model has recently gained much traction due to the COVID-19 pandemic since the public perception of vaccines plays a significant role in disease dynamics. This paper studies the vaccination game in the thermodynamic limit with an analytical method derived from the 1D Ising model called Nash equilibrium mapping. The individual dilemma regarding Vaccination comes from an internal conflict wherein one tries to balance the perceived advantages of immunizing with the apparent risks associated with Vaccination which they hear through different news media. We compare the results of Nash equilibrium(NE) mapping to other 1D Ising-based models, namely Darwinian evolution and agent-based simulation. This study aims to analyze the behaviour of an infinite population regarding what fraction of people choose to vaccinate or not vaccinate. While Nash equilibrium mapping and agent-based simulation agree mostly, Darwinian evolution strays far from the two models. It fails to predict the equilibrium behaviour of players in the population reasonably. We apply the results of our study to analyze the Astra-Zeneca(AZ) COVID-19 vaccine risk versus disease deaths debate, both via NE mapping and agent-based method. Both predict near 100% AZ vaccine coverage for people above 40, notwithstanding the risk. At the same time, younger people show a slight reluctance. We predict that while government intervention via vaccination mandates and advertisement campaigns is unnecessary for the older population, for the younger population (ages: 20-39), some encouragement from the government via media campaigns and vaccine mandates may be necessary.