Ethnicity and im/migrant classification systems and their constituent categories have a long history in the construction of public health knowledge on tuberculosis in the United Kingdom. This article critically examines the categories employed and the epidemiological discourses on TB, im/migrants, and ethnic minorities in health reporting between 1965 and 2015. We employ a Sociology of Knowledge Approach to Discourse Analysis to trace the continuities and changes in the categories used and in the discursive construction of im/migrants, ethnic minorities, and TB. These continuities and disjunctures are analysed within their socio-historical context to demonstrate the historical contingency of epidemiological knowledge production. We outline two historical phases in knowledge construction. The first coincides with the period of decolonisation, which witnessed a change in discursive identity ascriptions from ‘immigrants’ to ‘ethnic groups’ in health reporting as the ‘other’. The second commenced after 1991, when the adoption of the census ethnicity categories as a standard in the collection of population statistics entrenched ethnicity categories in health reporting. We argue the health reporting discourse reveals that the ‘new’ public health exhibits continuities with the ‘old’ by targeting the immigrant ‘other’ through biosecuritisation practices. We contend that these categories originated within a postcolonial paradigm and that increasing immigration and new forms of mobility are creating the preconditions for new discourses on identity construction that have implications for the current collaborative TB strategy.