Tuberculosis remains the leading cause of death among people living with HIV, and the imbalance is stark: HIV-positive individuals face roughly thirty times the risk of TB progression compared with the HIV-negative population. The clinical tool built to interrupt that pathway — TB preventive therapy, or TPT — has existed for decades, but a newer, shorter regimen is now reshaping how programs deliver it. The gap between what TPT can do and what it actually reaches is one of the more instructive coverage stories in global HIV/TB programming.
Why co-infection accelerates disease on both sides
HIV and tuberculosis reinforce each other in a way few co-infections do. HIV progressively weakens cell-mediated immunity, which is precisely the defense that normally contains a latent TB infection. As CD4 counts decline, the risk of latent TB reactivating — or of a new infection progressing straight to active disease — rises sharply. TB, in turn, accelerates HIV disease progression and complicates its treatment: co-infected patients face a higher burden of adverse drug events and often need longer, more carefully sequenced treatment courses. In high-burden settings, TB is described as the leading cause of death among people living with HIV, historically accounting for roughly three in ten HIV/AIDS-related deaths worldwide. Preventing TB before it becomes active disease is therefore not a peripheral intervention in HIV care — it is one of the interventions most directly tied to survival.
What TB preventive therapy is, and what changed
TPT is the practice of treating people at high risk of TB — principally those with latent infection or close TB exposure — before the disease becomes active and transmissible. The World Health Organization recommends it for people living with HIV who are unlikely to have active TB, regardless of their immune status, including those already on antiretroviral therapy, pregnant women, and people previously treated for TB.
For years the standard option was six to nine months of daily isoniazid (commonly written 6H or 9H). It worked, but long daily courses are hard to sustain: adherence dropped off over months, and cumulative toxicity was a real concern for both patients and the clinics tracking them. WHO guidance has since expanded to include shorter, rifapentine-based regimens as preferred alternatives — principally 3HP, three months of once-weekly isoniazid and rifapentine, and 1HP, one month of daily dosing with the same two drugs. The clinical case for both is essentially the same: comparable protective effect against TB, delivered in a fraction of the time and pill burden, which in practice means more people finish the course they start.
Comparing the regimen options
| Regimen | Duration | Dosing frequency | Main advantage |
|---|---|---|---|
| 9H (isoniazid) | 9 months | Daily | Long track record, low drug cost |
| 6H (isoniazid) | 6 months | Daily | Shorter than 9H, still daily-dosing burden |
| 3HP (isoniazid + rifapentine) | 3 months | Weekly | Far fewer doses; higher completion rates |
| 1HP (isoniazid + rifapentine) | 1 month | Daily | Shortest total course; useful where weekly follow-up is hard |
None of these regimens is universally correct. A program weighing them has to account for drug availability, interactions with specific antiretroviral regimens, pregnancy status, and how realistic weekly versus daily follow-up visits are in a given setting — which is exactly why WHO frames the shorter options as additional choices rather than a single mandated replacement.
Where the coverage gap actually sits
The clinical case for TPT is not in dispute; the implementation record is where the story gets harder. Recent estimates put global TPT coverage among people living with HIV at roughly 56 percent — well short of the 90 percent target that international bodies have set for the back half of this decade. That shortfall is not evenly distributed. It concentrates where drug supply is inconsistent, where clinics lack the systems to flag eligible patients at the point of an HIV visit, and where the shift from longer daily regimens to shorter rifapentine-based ones hasn’t yet reached procurement pipelines. A substantial share of people who are clinically eligible for TPT simply never start it, which is a different and in some ways more tractable problem than treatment failure — it is a systems gap, not a drug-efficacy gap.
The institutions financing and coordinating the response
Closing that gap runs through a small set of organizations whose roles are worth distinguishing. The World Health Organization sets the clinical guidelines — which regimens are recommended, for whom, and under what conditions. UNAIDS coordinates the broader HIV response and has historically driven the guidance linking intensified TB case-finding with preventive therapy at the country level. The Global Fund to Fight AIDS, Tuberculosis and Malaria is the largest multilateral financing vehicle for both diseases, investing billions of dollars annually across HIV and TB/HIV programs in low- and middle-income countries. PEPFAR, the U.S. President’s Emergency Plan for AIDS Relief, remains one of the largest single bilateral funders of HIV treatment and prevention infrastructure, and its funding decisions have historically shaped how quickly newer regimens like 3HP reach frontline clinics. None of these bodies delivers TPT directly to a patient; what they determine, collectively, is whether the drug reaches the shelf and whether the health worker in front of a patient has the guidance and the follow-up capacity to prescribe it.
The practical takeaway
TB preventive therapy for people with HIV is a case where the science has outpaced the delivery system. Shorter, rifapentine-based regimens like 3HP have removed much of the adherence burden that undermined the older nine-month course, and the WHO guidance embracing them has been in place for several years now. What remains is largely operational: getting the shorter regimens into consistent supply, building the clinic-level habit of screening every HIV patient for TPT eligibility rather than treating it as a special step, and sustaining the international financing that keeps both drugs and follow-up capacity available where the co-infection burden is highest. For a co-infection responsible for such a disproportionate share of HIV-related deaths, the preventive tool already exists. The work left is almost entirely about reach.