The effectiveness of vaccination programmes depends on high levels of public trust in political, scientific and health-related institutions, but public trust in vaccines can waver. This article explores aspects of public trust and mistrust on a web media platform about the MMR (measles-mumps-rubella) vaccine through the statements of a doctor and an anonymised ‘anti-vaxxer’. Thematic analysis identifies commonalities and divergences in both perspectives. Both trust and mistrust of MMR vaccination are presented as moral, reasoned stances by their proponents; they are (...) connected to the individual’s experiences and situations, but are associated with very different trust attitudes to scientific and political institutions. Moreover, both the trustworthiness of the speakers themselves and the (un)trustworthiness of authorities are emphasised. Trust and mistrust are also thematised in relation to contextual matters such as the role of social media and the historical MMR controversy. Further research towards identifying common ground between trust positions is recommended. (shrink)