Jab? No Thank You! Hesitancy and Free Riding in a Pandemic: Findings from COVID-19 in the EU

We develop a two-period model of the evolution of COVID-19. Individuals make choices about vaccination and social distancing. A subgroup of non-believers always rejects vaccination. We analyse two variants of the model: (i) freely chosen social distancing and (ii) an enforced minimum distancing rule. The model yields two notable results across multiple subgame-perfect equilibria. First, the zero-transmission threshold (ZTT) cannot be achieved in period 2 if it is not achieved in period 1. Second, a mixed strategy equilibrium may arise in which some individuals who are open to vaccination still refuse it. Using EU infection and vaccination data, we calibrate the model innovatively through reverse engineering. This allows us to estimate the expected costs of infection and vaccination (including side e¤ects), the size of the non-believer subgroup, and the strength of the minimum distancing rule. The estimates vary substantially across EU countries and across the two model variants. While the rst variant fails to nd any non-believers in 13 countries, the second indicates that non-believers were ubiquitous. Our framework also has applications beyond the COVID-19 pandemic