Defining tuberculosis vulnerability based on an adapted social determinants of health framework: a narrative review

The World Health Organization's new End TB Strategy emphasises socioeconomic interventions to reduce access barriers to TB care and address the social determinants of TB. To facilitate developing interventions that align with this strategy, we examined how TB vulnerability and vulnerable populations were defined in literature, with the aim to propose a definition and operational criteria for TB vulnerable populations through social determinants of health and equity perspectives. We searched for documents providing explicit definition of TB vulnerability or list of TB vulnerable populations. Guided by the Commission on the Social Determinants of Health framework, we synthesised the definitions, compiled vulnerable populations, developed a conceptual framework of TB vulnerability, and derived definition and criteria for TB vulnerable populations. We defined TB vulnerable populations as those whose context leads to disadvantaged socioeconomic positions that expose them to systematically higher risks of TB, but having limited access to TB care, thus leading to TB infection or progression to TB disease. We propose that TB vulnerable populations can be determined in three dimensions: disadvantaged socioeconomic position, higher risks of TB infection or progression to disease, and poor access to TB care. Examining TB vulnerability facilitates identification and support of vulnerable populations.