Public discord between those vaccinated and those unvaccinated for COVID-19 has intensified globally. Theories of intergroup relations propose that identifying with one’s social group plays a key role in the perceptions and behaviours that fuel intergroup conflict. We test whether identification with one’s vaccination status is associated with current societal polarization. The study draws on panel data from samples of vaccinated (n = 3,267) and unvaccinated (n = 2,038) respondents in Germany and Austria that were collected in December 2021 and February, March and July 2022. The findings confirm that vaccination status identification (VSI) explains substantial variance in a range of polarizing attitudes and behaviours. VSI was also related to higher psychological reactance toward mandatory vaccination policies among the unvaccinated. Higher levels of VSI reduced the gap between intended and actual counterbehaviours over time by the unvaccinated. VSI appears to be an important measure for predicting behavioural responses to vaccination policies.