Sustained effect of isoniazid preventive therapy among household contacts in Brazil.

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.

Sex and age differences in Mycobacterium tuberculosis infection in Brazil.

Globally, the prevalence of tuberculosis (TB) disease is higher in males. This study examined the effect of sex and age on Mycobacterium tuberculosis (Mtb) infection. Demographic and exposure data were collected on household contacts of sputum smear-positive pulmonary TB patients in Brazil. Contacts with tuberculin skin test induration ⩾10 mm at baseline or 12 weeks were considered Mtb infected. The study enrolled 917 household contacts from 160 households; 508 (55.4%) were female, median age was 21.0 years (range 0.30-87.0) and 609 (66.4%) had Mtb infection. The proportion infected increased with age from 63.3% in girls <5 years to 75.4% in women ⩾40 years and from 44.9% in boys <5 years to 73.6% in men ⩾40 years. Multivariable modelling showed the odds of infection increased between age 5 and 14 years among female contacts (OR 1.5 per 5-year age increase; 95% CI 1.1-2.2; P = 0.02) and between ages 0-4 and 15-39 years among male contacts (OR 2.7, 95% CI 0.83-8.9 and 1.1, 95% CI 0.99-1.3 per 5-year age increase; P = 0.10, 0.07, respectively). The study suggests that the age at which Mtb infection increases most is different in females compared with males. Studies are needed to explore whether these findings are due to differences in host susceptibility, exposure outside the household or other factors.