Sustained effect of isoniazid preventive therapy among household contacts in Brazil

C. Acuña-Villaorduña, E. C. Jones-López, P. Marques-Rodrigues, G. Fregona, M. Gaeddert, R. Ribeiro-Rodrigues, S. Vinhas, M. Palaci, P. Salgame, R. Dietze, J. Ellner

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5 Citations (Scopus)


BACKGROUND: Isoniazid preventive therapy (IPT) is highly effective in preventing TB disease; however, its long-term benefit in household contacts (HHCs) of infectious TB cases is unclear.METHODS: We conducted a retrospective analysis of two household contact studies in Vitoria, ES, Brazil, between 2008 and 2015. Households with smear-positive, culture-proven TB disease were enrolled. Eligible HHCs with tuberculin skin test (TST) indurations of ≥10 mm were referred to local TB clinics and IPT was started according to national guidelines. We reviewed the national dataset information system in January 2020 to identify HHCs with a diagnosis of TB disease. Time to event and Cox proportional regression analysis were conducted to identify factors associated with TB disease.RESULTS: Of the 1097 HHCs enrolled, 654 (60%) had TST ≥10 mm; 160 (24%) initiated IPT, of whom 115 (71.9%) completed IPT, which accounts for an overall completion rate of 18% among the population at risk; 42 (6%) TB cases were identified. IPT was associated with a 71% decrease in TB disease rates (HR 0.29, 95% CI 0.10-0.82; P = 0.02) among HHCs with TST ≥10 mm. IPT effect was sustained, as TB cases in HHCs without IPT occurred along the 7.9-year follow-up, whereas all four TB cases in HHCs with IPT were diagnosed within the first 3 years after exposureCONCLUSION: Isoniazid provides long-term protection for TB disease in household contacts of culture-proven TB cases.

Original languageEnglish
Pages (from-to)406-411
Number of pages6
JournalThe international journal of tuberculosis and lung disease : the official journal of the International Union against Tuberculosis and Lung Disease
Issue number5
Publication statusPublished - 1 May 2022


  • Mycobacterium tuberculosis
  • isoniazid
  • preventive therapy
  • household contacts
  • Brazil


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