BackgroundVaccination against Covid-19 has become an increasingly polarizing issue in western democracies. While much research has focused on social-psychological determinants of vaccine hesitancy, less is known about the attitudes and behaviors of the vaccinated populations towards those who are unvaccinated. Building on Weiner's attribution theory (2005, 1985, 1980), we predict that vaccination status determines the attribution of personal responsibility and blame in Covid-19 social dilemmas. This in turn explains people's affective and behavioral responses towards those who have fallen ill or infected others with COVID-19. ApproachThrough two preregistered experiments (total N = 1200) we show that people attribute greater personal responsibility when unvaccinated (vs. vaccinated) people fall ill from, or infect others with COVID-19. This attribution of responsibility manifested in less sympathy towards unvaccinated COVID-19 patients, which was associated with a lower willingness to help patients and their families (Study 1). Likewise, higher perceived responsibility results in greater anger towards unvaccinated people who had (involuntarily) infected others with the virus, which was associated with a greater desire for punitive actions (Study 2). ConclusionThese findings suggest that unvaccinated people experience blame as well as negative attitudes and behaviors from the vaccinated population. This could in turn strengthen people's refusal to get vaccinated and increase polarization between vaccine supporters and vaccine critics.