24 September 2026 Punjab Khabarnama Bureau : The protective effect of tuberculosis preventive treatment (TPT) may begin to weaken after about a year in countries with a high burden of TB, while the benefit appears to last considerably longer in medium- and low-burden settings, according to a new study.
The findings, published in The Lancet Respiratory Medicine, suggest that while preventive treatment provides strong protection during the first 12 to 24 months, its effectiveness against TB disease may decline sooner in high-transmission environments.
Strong Protection During First Year
TPT uses antibiotics to prevent people with inactive or latent TB infection from developing active TB disease.
The new study found that preventive treatment offered substantial protection during the first year or two across settings with different levels of TB burden. However, the duration of protection varied depending on the background level of TB transmission in the country.
Protection May Wane Earlier in High-Burden Countries
Researchers found that the protective effect could begin to decline after roughly one year in high-TB-burden countries.
By comparison, protection was reported to persist for around eight years in medium-burden settings and 13 years in low-burden countries.
The difference may partly reflect continued exposure to TB bacteria in places where transmission remains high, meaning people who have completed preventive treatment can potentially be exposed again.
What Is TB Preventive Treatment?
TB preventive treatment is given to people who have TB infection but do not have active TB disease.
The World Health Organization recommends TPT for groups at particularly high risk of progressing to active TB, including people living with HIV and household contacts of people diagnosed with TB, as well as certain other high-risk groups.
The objective is to eliminate or suppress TB bacteria before they can cause active disease.
Why High-Burden Settings Are Different
In countries where TB transmission is widespread, completing a course of preventive treatment does not necessarily eliminate the possibility of new infection later.
This distinction is important: a reduction in protection over time does not necessarily mean that the original treatment has simply “stopped working.” Continued exposure to TB bacteria can contribute to infections occurring after treatment.
Earlier Research Also Found Declining Protection
Other research has similarly examined how the effectiveness of preventive treatment changes over time.
A large individual-participant meta-analysis involving 6,668 contacts exposed to multidrug-resistant TB across 17 countries found that isoniazid preventive treatment reduced incident TB overall. The estimated reduction was greatest during the first year and declined during the second year, with the evidence becoming statistically uncertain after two years.
The findings reinforce the importance of considering the duration of protection alongside the level of ongoing TB exposure.
TPT Remains an Important Prevention Tool
The new findings do not suggest abandoning preventive treatment.
WHO continues to describe TPT as a critical component of efforts to prevent progression from TB infection to disease. Its guidelines emphasise identifying people at high risk, ruling out active TB before treatment, selecting an appropriate preventive regimen, supporting adherence and monitoring outcomes.
India Among Countries Using Preventive Treatment
India is among the countries implementing TB preventive treatment programmes.
WHO data show that global TPT coverage has increased in recent years, although it remains below the target set for high-risk populations. In 2024, an estimated 5.3 million people globally received TPT, up from 4.7 million in 2023.
India is also among countries using the six-month levofloxacin regimen recommended for certain contacts of people with multidrug-resistant TB.
Need for Stronger Follow-Up
The findings highlight the importance of continued TB surveillance after preventive treatment, particularly in high-burden settings.
Household contacts and other high-risk individuals may require continued monitoring for symptoms and timely evaluation if they develop signs of TB.
WHO recommends a comprehensive prevention approach rather than relying on medication alone, including identifying high-risk people, screening for active disease and ensuring appropriate treatment and follow-up.
Broader Implications for TB Control
The study adds to evidence that TB prevention strategies may need to account for local transmission intensity and the possibility of reinfection.
In high-burden countries, combining TPT with early diagnosis, contact tracing, infection-control measures and broader efforts to reduce TB transmission could be important for sustaining progress.