Background: The duration of the protective effect of TB preventive therapy (TPT) is controversial. Some studies have found that the protective effect of TPT is lost after cessation of therapy among people living with HIV in settings with very high tuberculosis incidence, but others have found long-term protection in low incidence settings.
Methods: We estimated the incidence rate (IR) of new tuberculosis disease (TB) for up to 12 years after randomization to four months of rifampin or nine months of isoniazid, among 991 Brazilian participants in a TPT trial in the state of Rio de Janeiro, with incidence 68.6/100,000 population in 2022. Adjusted hazard ratios (aHR) of independent variables for incident TB were calculated.
Results: Overall TB incidence rate (IR) was 1.7 (1.01; 2.7)/1,000 person years (PY). The TB IR among those who did not complete TPT was higher than in those who completed [2.9/1000 PY (95% CI: 1.3; 5.6) versus 1.1/1000 PY (95% CI: 0.4; 2.3), IR ratio (IRR)= 2.7 (95% CI: 1.0; 7.2)]. TB IR was higher within 28 months after randomization [IR: 3.5/1000 PY (1.6; 6.6) PY, compared to 1.1/1000 PY (95% CI: 0.5; 2.1) between 28 and 143 months, IRR= 3.1, 95% CI: 1.2-8.2]. Treatment non-completion was the only variable associated with incident TB [aHR= 3.2 (1.1; 9.7)].
Conclusion: In a mostly HIV non-infected population, a complete course of TPT conferred long-term protection against tuberculosis.
Keywords: Mycobacterium tuberculosis; Brazil; isoniazid; latent tuberculosis infection; rifampicin.
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