HIV treatment as prevention: natural experiments highlight limits of antiretroviral treatment as HIV prevention

Abstract

There is growing enthusiasm for increasing coverage of antiretroviral treatment among HIV-infected people for the purposes of preventing ongoing transmission. Treatment as prevention will face a number of barriers when implemented in real world populations, which will likely lead to the effectiveness of this strategy being lower than proposed by optimistic modelling scenarios or ideal clinical trial settings. Some settings, as part of their prevention and treatment strategies, have already attained rates of HIV testing and use of antiretroviral therapy--with high levels of viral suppression--that many countries would aspire to as targets for a treatment-as-prevention strategy. This review examines a number of these "natural experiments", namely, British Columbia, San Francisco, France, and Australia, to provide commentary on whether treatment as prevention has worked in real world populations. This review suggests that the population-level impact of this strategy is likely to be considerably less than as inferred from ideal conditions.

Figure 1. Series of steps required in order to reduce onward transmission from someone infected with HIV.

Figure 2. Estimated number of people living with HIV in Australia and per capita transmission rate over time.

The per capita transmission rate is defined as the average number of new onward HIV infections resulting from each HIV-infected person per year; this is calculated as the number of new diagnoses in a given year (as a surrogate marker for incidence) divided by the estimated number of people living with HIV (PLHIV).