Results from two studies reveal that a daily antiretroviral tablet taken by people who do not have HIV infection can reduce their risk of acquiring HIV by up to 73%. Both daily tenofovir and daily tenofovir/emtricitabine taken as preventive medicine (PrEP – pre-exposure prophylaxis) can prevent heterosexual transmission of HIV from men to women and from women to men.
There were 62% fewer HIV infections in the group receiving tenofovir and 73% fewer HIV infections in the group that took tenofovir /emtricitabine than in the group receiving the placebo.
http://www.who.int/hiv/mediacentre/prep_20110713/en/index.html#.T5WzqdY-aC0.facebook