Preventive treatment for tuberculosis (TB) is crucial in stopping latent TB infections from developing into potentially deadly TB disease. Despite TB infection being fully treatable, there is currently no consensus globally on which subgroups of individuals exposed to TB should be prioritized for preventive treatment, or if the benefits of such treatment vary based on factors such as age or confirmed infection status. A Boston University School of Public Health (BUSPH) study led by Dr. Leonardo Martinez aimed to provide clarity on this issue, specifically focusing on the effectiveness of preventive treatment in exposed individuals.
The study found that in settings with low TB prevalence, priority should be given to exposed individuals with confirmed TB infection, regardless of their age. On the other hand, in high TB-burden settings, all exposed individuals should be considered for preventive treatment, even without confirmation of infection. This strategy could potentially help in ending the tuberculosis epidemic and support global public health efforts to reduce TB mortality by 95 percent by 2035. Dr. Martinez emphasized the importance of finding ways to optimize prevention in tackling the TB epidemic, as it affects tens of millions of people every year and has long-lasting effects even after individuals recover.
The study included a comprehensive review and analysis of new TB cases among individuals who were in close contact with diagnosed TB patients. The team compared the effectiveness of preventive treatment in these exposed individuals based on age, infection status, and the burden of TB in their respective settings. The findings showed that preventive TB treatment was 49 percent effective among the 2,496 individuals who developed TB, with a particularly high effectiveness of 80 percent in individuals with a positive skin or blood test. Notably, preventive treatment was not effective in most individuals without evidence of infection, except for children under 5.
The study also revealed that the effectiveness of preventive treatment was comparable across all age groups – adults, children ages 5-17, and children under 5 – for individuals with a positive skin or blood test. Additionally, the treatment was more effective in high-burden settings compared to low-burden settings. The researchers estimated the number of individuals needed to receive treatment in order to prevent one person from developing TB disease, with a lower number needed in high-burden settings (29 to 43 individuals) compared to low-burden settings (213 to 455 individuals).
Despite the fact that individuals with negative blood or skin tests do not appear to benefit from preventive treatments, the researchers suggest that the overall low number needed to treat may justify prioritizing this treatment for all exposed contacts in settings where testing for TB infection is inaccessible. Dr. C. Robert Horsburgh, a study coauthor and professor of global health, emphasized the importance of treating individuals with latent TB in order to ultimately end the threat of global TB. The study’s results highlight the effectiveness of preventive treatment in preventing TB disease development and the importance of prioritizing treatment in certain exposed populations.