Increasing COVID-19 vaccination intentions: a field experiment on psychological ownership

Abstract

With the increasing availability of life-saving vaccines against the SARS-CoV-2 virus, government agencies face the challenge of promoting vaccine uptake. Thus, encouraging vaccine uptake marks an urgent policy challenge in fighting the COVID-19 pandemic. This study builds on the theory of psychological ownership to design a behaviorally inspired local government vaccination campaign. We conducted a large-scale, cluster-randomized field experiment (N = 27,298 residents nested in 6,442 addresses) delivered to all registered residents of a German municipality via an official mailing campaign. The campaign included a psychological ownership intervention designed to boost residents’ intentions to get vaccinated – measured through unique link clicks on a municipal website where people can schedule a COVID-19 vaccination appointment. Findings suggest that adding possessive pronouns (i.e., ‘YOUR vaccination’) increases vaccination intentions by 39%, or 2.5 percentage points (p < 0.0001 [95% CI = 1.8%, 3.3%], control letter: 6.4%, treatment letter: 8.9%). The discussion outlines the value of using psychological ownership-based nudge interventions to increase vaccine uptake and other desirable behaviors.