In the United States, an estimated 48,100 new human immunodeficiency virus (HIV) 
infections occurred in 2009. Of these, 27% were in heterosexual men and women 
who did not inject drugs, and 64% were in men who have sex with men (MSM), 
including 3% in MSM who inject drugs. In January 2011, following publication of 
evidence of safety and efficacy of daily oral tenofovir disoproxil fumarate 300 
mg (TDF)/emtricitabine 200 mg (FTC) (Truvada, Gilead Sciences) as antiretroviral 
preexposure prophylaxis (PrEP) to reduce the risk for HIV acquisition among MSM 
in the iPrEx trial, CDC issued interim guidance to make available information 
and important initial cautions on the use of PrEP in this population. Those 
recommendations remain valid for MSM, including MSM who also have sex with 
women. Since January 2011, data from studies of PrEP among heterosexual men and 
women have become available, and on July 16, 2012, the Food and Drug 
Administration (FDA) approved a label indication for reduction of risk for 
sexual acquisition of HIV infection among adults, including both heterosexuals 
and MSM. This interim guidance includes consideration of the new information and 
addresses pregnancy and safety issues for heterosexually active adults at very 
high risk for sexual HIV acquisition that were not discussed in the previous 
interim guidance for the use of PrEP in MSM.