About one in four people worldwide — approximately 2 billion — are infected with Mycobacterium tuberculosis, including approximately 13 million in the United States. Most have latent TB infection (LTBI): no symptoms and not contagious. But without treatment, approximately 5%–10% develop TB disease in their lifetime, and progression from untreated latent infection accounts for approximately 80% of U.S. TB cases. Treating latent TB prevents that.
The previous comprehensive U.S. guidelines dated from 2000. In 2020 the National Tuberculosis Controllers Association (NTCA) and CDC issued updated ones.
How the guidelines were made
A committee of experts ran a systematic review of clinical trials — 55 trials of effectiveness and 31 of toxicity — plus a network meta-analysis of 63 studies of 16 regimens to compare treatments never tested head-to-head. Effectiveness meant preventing TB disease; toxicity meant liver damage (the one side effect comparable across studies). Evidence was graded with the GRADE system: strong recommendations need at least moderate evidence that benefits outweigh harms for most patients; conditional ones reflect more uncertainty.
The five recommended regimens
All apply to TB presumed susceptible to isoniazid or rifampin — not to strains resistant to both.
| Regimen | Status | For |
|---|---|---|
| 3 months of once-weekly isoniazid + rifapentine | preferred, strong | adults and children over 2, including people with HIV (drug interactions allowing) |
| 4 months of daily rifampin | preferred, strong | HIV-negative adults and children of all ages |
| 3 months of daily isoniazid + rifampin | preferred, conditional | adults and children of all ages, including people with HIV (drug interactions allowing) |
| 6 months of daily isoniazid | alternative | strong for HIV-negative people; conditional for people with HIV |
| 9 months of daily isoniazid | alternative | conditional, for adults and children with or without HIV |
The short rifamycin-based regimens are preferred because they work as well, are safer, and are more often completed. Isoniazid alone works but is more toxic and less often finished, which lowers its real-world effectiveness.
Caution: rifampin and rifapentine are easy to confuse but not interchangeable — prescribers and pharmacists must make sure patients get the right drug.
The regimens in detail
Weekly isoniazid plus rifapentine. Given by directly observed therapy, it was as effective as, and no more toxic than, 9 months of isoniazid, with higher completion. Downsides: higher drug cost, possible costs of observed therapy, 10 pills at once each week, and a flu-like systemic reaction that can include fainting and low blood pressure — severe enough for hospitalization in 0.1% of people, usually mild and self-limited, with no deaths reported. Self-administered therapy is an approved option.
Daily rifampin. Equivalent effectiveness to 9 months of isoniazid, with less liver toxicity, fewer stops for side effects and higher completion. There is no evidence yet for people with HIV. Rifamycins interact with many drugs — including warfarin, oral contraceptives, azole antifungals and HIV medicines; rifabutin may substitute when rifampin can’t be used and isoniazid isn’t an option. In people with HIV and low CD4 counts, undetected TB disease treated with rifampin alone risks resistance.
Daily isoniazid plus rifampin. Similar risk of TB disease, liver damage and stopping for side effects as 6 or more months of isoniazid, including in children under 15 and people with HIV; the two drugs together may carry more liver risk than either alone.
Isoniazid alone. Reduces TB risk in people with a positive skin test, adults and children, with and without HIV; side effects are more common in adults. In people with HIV who have a negative or unknown skin test in low-TB settings, the benefit is uncertain. No trial directly compares 9 months with 6 or 12. In high-TB settings, isoniazid plus antiretroviral therapy prevents more TB than either alone.
Not recommended: 2 months of rifampin plus pyrazinamide, because of severe liver toxicity — though people started on four-drug TB treatment who turn out to have only latent infection are effectively treated.
What the guidelines don’t cover
They weren’t based on cost-effectiveness, don’t address who to test or how to run programs, and are written for low-TB-incidence countries. Short regimens should not be used when rifamycins are contraindicated, such as with major drug interactions. Local and state TB programs can advise on individual cases.
Bottom line: for patients without drug intolerance or interactions, 3–4 months of a rifamycin-based regimen is preferred over 6–9 months of isoniazid.
Sources
Based on Sterling TR, Njie G, Zenner D, et al., "Guidelines for the Treatment of Latent Tuberculosis Infection: Recommendations from the National Tuberculosis Controllers Association and CDC, 2020," MMWR Recommendations and Reports Vol. 69, No. 1, CDC; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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