By Arleen A. Leibowitz, Ph.D.

The iPrEx trail results published in NEJM at the end of December were hailed as the start of a new era in the prevention of HIV infection. iPrEx studied pre-exposure prophylaxis (PrEP)— the regular use of antiretroviral medications by uninfected individuals—in a sample of MSM in several countries. Dramatic as these results were—PrEP reduced HIV incidence by 44% in the clinical trial—we need to be cautious about how we implement PrEP lest we abandon proven prevention strategies that can prevent greater numbers of HIV infections with the same level of expenditure as PrEP.

PrEP has been called the “next big thing” and Bill Gates has said that if the trials are successful PrEP distribution programs could start in 2012 in developing countries (Bennett 2010). Before launching any widespread dissemination of PrEP, policy makers need to decide how PrEP fits into an overall strategy for HIV prevention. PrEP is very costly because it depends on ARVs actively used in HIV treatment. Although these drugs would be less expensive in developing countries, developing countries’ ability to pay for drugs is also correspondingly lower. PrEP’s high cost means that its widespread dissemination would likely displace other prevention strategies, such as condom use, post-exposure prophylaxis (PEP), microbicides (CAPRISA) or Testing plus Linkage to Care (TLC+), that could prevent greater numbers of infections at lower cost.

Modeling suggests that compared to PrEP, TLC+ is more cost effective (Long; Paltiel; Walensky). The economic argument is supported by an ethical argument: shouldn’t our first priority be to provide ARVs to all who already are infected with HIV, rather than those the uninfected? Indeed, I believe that the ethical approach is to prevent as many new infections as possible with given tools. This will require us to prioritize our prevention strategies and make the most effective strategies the first line of defense.