Vaccination is a social act, where benefits spill-over to third parties. How we approach such social decisions is influenced by whether likely beneficiaries share salient social identities with us. This study explores these dynamics using representative survey data from two contexts: national identity groups in Wales (N=4187) and political partisans in America (N=4864).
In both cases, those in the minority in their local area were less likely to be vaccinated. In Wales, respondents who did not identify as Welsh were less likely to be vaccinated the greater the proportion of residents of their local area identified as Welsh. In America, the vaccination rate of Biden voters fell off more steeply than that of Trump voters as the proportion of Trump voters in their county increased. Results are robust to controlling for likely confounds and sensitivity analyses. In-group out-group dynamics help to shape important health decisions.