This article analyses the politicisation of public health debates by focusing on vaccination and mental health care in the Czech Republic. The mainstream understanding of politicisation commonly refers to politics-as-sphere, linked with the political instrumentalisation of health care controversies as part of electoral campaigning and power struggles. In our analysis, we conceive politicisation more broadly, as politics-as-activity, which encompasses the role of civic engagement and the involvement of patients in these processes. We thus view politicisation as a process which encompasses a plurality of political actors and, in addition to politicians, includes patients, users, carers, citizens, and experts. Our analysis draws on extensive empirical evidence, consisting of observations, semi-structured interviews, and a review of available documents. The study took place in the Czech Republic from 2017 to 2019. We conclude that politicisation takes place alongside four dimensions: (1) contingency, (2) agency, (3) a plurality of opinions and approaches, and (4) visibility. We further argue that the contingent nature of biomedical controversies is articulated in three different, possibly interconnected layers. Thus, the politicisation of the two Czech analysed cases refers to (a) uncertainties and problematic aspects of biomedical objects of controversy; to (b) social rights, economic needs, and legal aspects as well as social representations of illness and vaccinations in the public debate; and to (c) the political processes which determine the previous two layers of politicisation, labelled as meta-politicisation. Last but not least, we stress the dynamic and non-linear nature of politicisation processes, the varieties of connections between the third sector and expertise, and the necessity to analyse the politicisation of public health controversies hand in hand with its connection to depoliticisation and repoliticisation. Copyright © 2021 Elsevier Ltd. All rights reserved.