I am HIV- and my partner is HIV+. We practise safe sex. There have been new CDC guidelines issued for accidental exposure and HAART therapy. Should I consider HAART prophylaxis if there is condom failure when I am the anal receptive partner? My partner is on therapy and has an undetectable viral load. It appears to me that the innoculum he might expose me to in this case would not warrant the risk of HAART.

The following is the summary of recommendations from the U.S. Department of Health and Human Services (from January, 20005) that is posted on the CDC website.

The most effective means of preventing human immunodeficiency virus (HIV) infection is preventing exposure. The provision of antiretroviral drugs to prevent HIV infection after unanticipated sexual or injection-drug--use exposure might be beneficial. The U.S. Department of Health and Human Services (DHHS) Working Group on Nonoccupational Postexposure Prophylaxis (nPEP) made the following recommendations for the United States. For persons seeking care <72 hours after nonoccupational exposure to blood, genital secretions, or other potentially infectious body fluids of a person known to be HIV infected, when that exposure represents a substantial risk for transmission, a 28-day course of highly active antiretroviral therapy (HAART) is recommended. Antiretroviral medications should be initiated as soon as possible after exposure. For persons seeking care <72 hours after nonoccupational exposure to blood, genital secretions, or other potentially infectious body fluids of a person of unknown HIV status, when such exposure would represent a substantial risk for transmission if the source were HIV infected, no recommendations are made for the use of nPEP. Clinicians should evaluate risks and benefits of nPEP on a case-by-case basis. For persons with exposure histories that represent no substantial risk for HIV transmission or who seek care >72 hours after exposure, DHHS does not recommend the use of nPEP. Clinicians might consider prescribing nPEP for exposures conferring a serious risk for transmission, even if the person seeks care >72 hours after exposure if, in their judgment, the diminished potential benefit of nPEP outweighs the risks for transmission and adverse events. For all exposures, other health risks resulting from the exposure should be considered and prophylaxis administered when indicated. Risk-reduction counseling and indicated intervention services should be provided to reduce the risk for recurrent exposures.

See the following website for the full Report: Centers for Disease Control

I think that the scenario you describe is an example of appropriate use of PEP, if it is done within 72 hours after exposure. While a well controlled viral load can reduce the risk of transmission, it does not eliminate the risk. I recommend that you and your partner speak about this with his and/or your physician. You need to understand all of the issues involved. And I suggest that you develop a plan as to how you would go about taking PEP if an accident (e.g., condom break when you are the receptive partner) occurs, since time is crucial if you are to initiate the therapy following the exposure.