Men who have sex with men (MSM)
The iPrEx study was a double-blind, placebo-controlled, multi-centre trial. The TDF/FTC treatment group, who took the PrEP regularly, was associated with a 44% reduction in the risk of HIV acquisition (95% CI, 15-63). When blood samples were tested for the medication, there was a 92% reduction in the risk of HIV acquisition in persons with detectable levels of TDF/FTC versus those without.
The IPERGAY study was a double-blind, multi-centre trial. The on-demand regimen involved taking 2 tablets of TDF/FTC 2 to 24 hours before sex, 1 tablet a day during periods of sexual risk and for 48 hours (two doses) after sex.
The study was stopped early when it showed that 14 people became infected with HIV in the placebo group compared with 2 in the TDF/FTC group, a risk reduction of 86%.
The PROUD study was a randomised, open-label trial in England. A total of 23 participants became infected with HIV over the course of the study; three in the daily TDF/FTC group and 20 in the deferred group. This represents a risk reduction of 86%.
Heterosexuals
The Partners PrEP trial was a double-blind trial of daily TDF/FTC or TDF in Uganda and Kenya conducted from 2008 to 2010. Compared to placebo, the overall efficacy estimates was 75% for TDF/FTC, and 67% for TDF alone. When blood TDF levels were measured, for participants in the TDF/FTC group, detectable drug was associated with a 90% reduction in the risk of HIV acquisition.