1. Background

Latent tuberculosis infection (LTBI) is defined as a state of persistent immune response to stimulation by M. tuberculosis antigens with no evidence of clinically manifest active TB (1)³ . As there is no “gold standard” test for TB infection, the global burden is not known with certainty; however, about one fourth of the world’s population is estimated to be infected with M. tuberculosis (2),(3). The vast majority have no signs or symptoms of TB disease and are not infectious, although they are at risk of developing active TB disease and becoming infectious. Several studies have shown that in recent decades, on average, 5–10% of those infected will develop active TB disease over the course of their lives, usually within the first 5 years after initial infection (4),(5). The risk for active TB disease after infection depends on several factors, the most important being immunological status (1). At the first United Nations high-level meeting on TB in 2018, Member States committed to provide TB preventive treatment to at least 30 million people in 2018–2022: 6 million people living with HIV (People with HIV), 4 million children < 5 years who are household contacts of people with TB, and 20 million other household contacts (6).

Prevention of active TB disease by TB preventive treatment is a critical component of the WHO End TB Strategy and efforts to eliminate TB (7),(8),(9). The efficacy of currently available TB preventive treatment ranges from 60% to 90% (1). The potential benefit of treatment should, however, be carefully balanced against the risk for drug-related adverse events. Mass, population-wide LTBI testing and treatment are not feasible because the tests are imperfect, there are risks of serious and potentially fatal adverse drug reactions, with a high cost and unproven public health impact. The benefits of TB preventive treatment are more likely to outweigh harms in infected individuals belonging to population groups in whom the risk for progression to active disease significantly exceeds that of the general population. The programmatic management of TB preventive treatment (PMTPT) involves a comprehensive package of interventions: identifying and testing those individuals who should be tested, delivering effective, safe treatment in such a way that the majority of those starting a treatment regimen will complete it with no or minimal risk of adverse events, and monitoring and evaluation of the process. PMTPT fits within a larger framework of preventive actions envisaged by Pillars 1 and 2 of the End TB Strategy, ranging from screening for active TB, infection control, prevention and care of HIV and other co-morbidities and health risks, access to universal health care, social protection and poverty alleviation.

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