24 September 2026 Punjab Khabarnama Bureau : Protection provided by tuberculosis preventive treatment (TPT) may begin to decline after about one year in countries with a high burden of TB, while the benefits can last much longer in medium- and low-burden settings, according to a major international study published in The Lancet Respiratory Medicine.
The study analysed individual-level data from 84,128 people across 24 countries, drawn from 44 cohort studies. Researchers examined people with evidence of Mycobacterium tuberculosis infection who had been exposed to TB, comparing the risk of developing active disease after preventive treatment.
Strong Protection During the First Year
Researchers found that TPT provided substantial protection during the first 12 months, across countries with different levels of TB transmission.
However, the duration of that protection varied considerably according to the background TB burden. In high-burden settings, the protective effect declined relatively quickly, while stronger long-term protection was observed in medium- and low-burden settings.
At one year, the adjusted hazard ratio for developing TB was 0.57 in high-burden settings, compared with 0.14 in medium-burden countries and 0.21 in low-burden countries.
Protection Lasted Much Longer in Lower-Burden Settings
The study found that the benefit of TPT remained evident for at least eight years in medium-burden settings and up to 13 years in low-burden settings.
In medium-burden countries, the adjusted hazard ratio remained 0.15 at eight years. In low-burden settings, protection was still evident at 13 years, although the confidence interval was wider.
The researchers said the findings demonstrate that a single course of preventive treatment can have long-lasting benefits in settings where ongoing exposure to TB is less common.
Why Protection May Decline Faster in High-Burden Areas
One possible explanation is re-exposure and reinfection.
TPT treats existing TB infection and reduces the risk that it will progress to active disease, but it does not provide permanent protection against becoming infected again.
In communities where TB transmission remains high, people may encounter the bacteria repeatedly after completing treatment. Researchers said this ongoing exposure is likely to contribute to the faster decline in protection observed in high-burden settings.
TPT Is Still an Important TB Prevention Tool
The findings do not mean that preventive treatment is ineffective.
Researchers emphasised that TPT remains highly effective at preventing TB from progressing from infection to active disease, particularly during the period immediately after infection and treatment.
Instead, the study suggests that TPT should not necessarily be viewed as a standalone solution in places where community transmission remains high.
Combination of Prevention Measures Needed
For high-burden countries, the researchers recommend combining TPT with other measures aimed at reducing ongoing transmission.
These can include early detection and treatment of active TB, contact tracing, infection prevention and control, improved screening and broader public-health interventions.
The study’s lead author, Lauren Linde of Boston University School of Public Health, said the rapid decline in protection in very high-burden settings strengthens the case for addressing ongoing community transmission alongside TPT.
India Among High-Burden Countries
India is classified as a high-TB-burden country, making the findings particularly relevant to its TB-control efforts.
The study included participants from multiple countries and settings, but its results do not mean that every person receiving TPT in India will lose protection after one year. Individual risk depends on factors including exposure, infection status and the local level of transmission.
WHO Continues to Promote Preventive Treatment
The World Health Organization considers TPT an important part of global efforts to reduce TB infections and deaths.
WHO data show that the number of people receiving TPT globally has increased substantially in recent years, reaching 5.3 million in 2024. However, coverage among household contacts and people living with HIV remained below global targets.
Study Highlights Need for Long-Term Protection
The researchers said more work is needed to understand exactly why the protective effect of TPT declines faster in high-burden settings.
The findings nevertheless provide important evidence for designing TB-control strategies that account for differences in local transmission. In areas with continued high exposure, preventing new infections may be just as important as treating existing latent infections.
A Broader Lesson for TB Control
The study suggests that the effectiveness of TB prevention cannot be assessed solely by whether an individual completes a medication course.
The surrounding environment also matters. Where TB transmission remains high, people who have completed preventive treatment can continue to face the possibility of new exposure.
For high-burden countries such as India, researchers therefore point towards a combined approach involving preventive treatment and stronger efforts to reduce community transmission.