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TB Preventive Treatment Offers Durable Protection in Low- and Medium-Burden Settings, but Erodes Rapidly in High-Burden Countries
In the largest individual-participant meta-analysis of its kind, tuberculosis preventive treatment (TPT) reduced tuberculosis incidence by approximately 86% in medium-burden settings and 79% in low-burden settings within the first year (adjusted HR 0.14 [95% CI 0.09–0.21] and 0.21 [95% CI 0.17–0.26], respectively), with protection persisting for up to 8–13 years. In contrast, protection in high-burden settings was substantially weaker at one year and was not statistically significant (adjusted HR 0.57 [95% CI 0.31–1.07]), suggesting that background tuberculosis exposure critically shapes how long preventive treatment remains effective.
What Was Studied
This analysis examined whether tuberculosis preventive treatment protects against incident tuberculosis over time, and specifically whether the duration of that protection varies depending on the tuberculosis burden of the setting in which recipients live. The primary outcome was incident tuberculosis diagnosed more than 90 days after baseline enrollment among close contacts who tested positive for Mycobacterium tuberculosis infection at baseline.
How It Was Studied
Researchers conducted a systematic review and individual-participant meta-analysis, pooling data from 44 cohort studies across 24 countries, ultimately including 84,128 individuals who were close contacts of tuberculosis cases and had confirmed M. tuberculosis infection at baseline. Settings were stratified by national tuberculosis incidence into low-burden (<20 per 100,000), medium-burden (20–100 per 100,000), and high-burden (>100 per 100,000) categories. The comparator group comprised individuals who received no TPT or did not complete TPT. Mixed-effects Cox models incorporating a time interaction were used to generate adjusted hazard ratios, and Nelson-Aalen cumulative hazard plots were used to visualize protection over follow-up periods extending up to 13 years.
What Was Observed
- Strong early protection in low- and medium-burden settings: At one year, TPT recipients in medium-burden settings had approximately 86% lower tuberculosis risk than untreated contacts (adjusted HR 0.14 [95% CI 0.09–0.21]), and those in low-burden settings had approximately 79% lower risk (adjusted HR 0.21 [95% CI 0.17–0.26]). These are large, precisely estimated effects with narrow confidence intervals.
- Protection in medium-burden settings sustained for at least 8 years: The protective effect in medium-burden countries did not meaningfully erode over time, with an adjusted HR of 0.15 (95% CI 0.07–0.33) at 8 years — essentially unchanged from the one-year estimate — indicating durable and sustained benefit over the long term.
- Low-burden setting protection persists but narrows by 13 years: In low-burden settings, protection remained statistically borderline at 13 years (adjusted HR 0.65 [95% CI 0.43–1.00]), suggesting gradual attenuation over time though still indicating a meaningful protective trend through more than a decade of follow-up.
- Completion of TPT confers greater initial benefit but similar long-term outcomes: Among participants in low- and medium-burden settings, those who completed TPT had approximately 41% lower tuberculosis risk at one year compared with those who did not complete treatment (adjusted HR 0.59 [95% CI 0.36–0.95]); however, this difference was no longer statistically significant by two years (adjusted HR 0.72 [95% CI 0.41–1.26]), and both groups showed strong long-term protection, suggesting partial treatment may still confer substantial benefit.
Why This Matters
Millions of individuals at risk of tuberculosis receive preventive treatment each year, yet policies governing TPT duration and re-treatment eligibility have largely assumed uniform protection across all settings. These findings demonstrate that background tuberculosis incidence substantially modifies how long preventive treatment remains effective, with protection eroding relatively quickly in high-burden environments likely due to ongoing re-exposure. This evidence supports revisiting burden-stratified TPT policies and re-treatment protocols, particularly for individuals living in high-burden settings where the data suggest protection may be insufficient or short-lived.
How to Read This Result
This is a high-quality, large-scale individual-participant meta-analysis with a strong positive signal in low- and medium-burden settings; however, the predominance of observational cohort data across diverse countries introduces potential confounding, and the lack of statistical significance in high-burden settings — combined with heterogeneity in study designs and follow-up durations — warrants caution when applying these findings to specific populations or clinical protocols.
Limitations
The abstract does not explicitly report study limitations.