Undetectable viral load and HIV transmission dynamics on an individual and population level: where next in the global HIV response?

To examine recent literature on the efficacy and effectiveness of HIV treatment in preventing HIV transmission through sexual exposure, at both an individual and at a population level.

Two recent studies on the individual-level efficacy of treatment as prevention (TasP) have added to the now conclusive evidence that HIV cannot be transmitted sexually when the virus is suppressed. However, four large cluster-randomized population-level trials on universal HIV testing and treatment in Africa have not delivered the expected impact in reducing HIV incidence at a population level. Two of these trials showed no differences in HIV incidence between the intervention and control arms, one demonstrated a nonsignificant lower incidence in the intervention arm, and the fourth trial found a reduction between the communities receiving a combination prevention package and the control arm, but no difference between the immediate treatment plus the prevention package and the control arm. Factors contributing to the disconnect between individual high-level efficacy and population-level effectiveness of TasP include undiagnosed infection, delays in linkage to care, challenges in retention and adherence to antiretroviral therapy (ART), time between ART initiation and viral suppression, and stigma and discrimination.

Suppressive ART renders people living with HIV sexually noninfectious. However, epidemic control is unlikely to be achieved by TasP alone.