The findings are based on a mathematical model developed by researchers to predict the public-health impact of pre-exposure chemoprophylaxis (PrEP) – an HIV prevention strategy that uses antiretroviral drugs, currently given in combination to treat HIV-positive individuals, to stop the infection from occurring in the first place.

Through the model, the research team predicts that PrEP, targeted to those at highest behavioural risk, could have a major impact on public health, potentially preventing 3.2 million cases of HIV in southern sub-Saharan Africa alone in ten years. Sub-Saharan Africa, the epicentre of the HIV/AIDS global epidemic, contains almost 63 percent of the world’s HIV-infected population, totalling about 22.4 million adults.

PrEP is based on the hypothesis that HIV transmission can be curtailed if treatment is given before exposure to the infection occurs. Data from animal studies suggests that PrEP is an effective method to prevent HIV infection and it is now under study in human populations. The strategy has its detractors, however, who suggest that the availability and use of PrEP could cause sexual disinhibition in which individuals feel as though they no longer need to practice traditional methods of safe sex, including abstinence, using condoms and limiting sexual partners.

In an optimistic scenario in the model in which PrEP was effective 90 percent of the time and used by 75 percent of the sexually active population, it could potentially cut new HIV infections by 74 percent in sub-Saharan Africa, if used constantly for ten years. In a pessimistic scenario in which PrEP was effective 30 percent of the time and used by 25 percent of the sexually active population the benefits were significantly lessened with only a 3.3 reduction.; Source: University of Pittsburgh Schools of the Health Sciences