Has PrEP Been Proven Effective?

Editor's Note: There are, unfortunately, many myths going around about pre-exposure prophylaxis, or PrEP -- the use of an antiretroviral drug by HIV-negative people to prevent them from being infected with HIV during sex. This month we'll look at one myth per day and offer evidence why it's not true.

Myth 2: PrEP hasn't been proven effective.

Truth: Several studies on the use of Truvada for pre-exposure prophylaxis, or PrEP, have shown that when taken as directed it can vastly reduce the chance of infection. That held true for gay men, heterosexual couples, and injection-drug users. In the multinational Preexposure Prophylaxis Initiative (iPrEx) study of men who have sex with men, Truvada as PrEP, combined with other preventive services, reduced the risk of HIV infection by more than 90 percent. Even when taking a critical look at the studies, Josh Barro at The New York Times wrote, "Bear in mind, PrEP is about reducing the probability of an already low-probability event. If the participants in iPrEx not taking medication had a 3-4 percent chance of contracting H.I.V. in a given year, 99-percent effective daily use of PrEP would reduce their annual risk of infection to 0.04 percent, or 4 in 10,000. That happens to be equal to the risk of accidental death for the average American in a given year."