Modeling the implementation of population-level isoniazid preventive therapy for tuberculosis control in a high HIV-prevalence setting.

BACKGROUND

We model the epidemiological impact of providing isoniazid preventive therapy (IPT) to South African adolescents, among whom HIV prevalence is low, latent tuberculosis (TB) prevalence is high, and school-based programs may enable population-level coverage.

METHODS

We simulate a dynamic compartmental model of age-structured HIV and TB coepidemics in South Africa. HIV dynamics are modeled by infection status, CD4 cell count, and antiretroviral therapy; TB dynamics are modeled by disease stage, diagnosis, treatment, and IPT status. We analyze the effects of continuous IPT coverage among adolescents from 5 (baseline) to 90%.

RESULTS

Our model is calibrated to WHO and the Joint United Nations Programme on HIV/AIDS epidemiological estimates. In simulations, increasing IPT coverage to 50% among adolescents reduced active TB incidence by 5-34%. Increasing coverage to 90% led to a 9-40% reduction in active TB incidence. Expanded IPT access causes TB incidence to decline in the general population of HIV-positive individuals, as well as in adult HIV-positive individuals.

CONCLUSION

Targeting IPT to a secondary school population with high latent TB prevalence and low-HIV prevalence, in which risk of false-negative diagnosis of active TB is low and IPT benefits are more established, could have substantial benefits to adolescents and spillover benefits to the adult population.