Pre-Exposure Prophylaxis Efficacy

  

High levels of PrEP efficacy demanded by gay men before they consider it a replacement for condoms

Treatment as prevention
 
Michael Carter
Published: 10 August 2011
 
PrEP would need to provide near perfect levels of protection against infection with HIV in order for the majority of gay men to see it as a replacement for condoms for receptive anal sex, results of a US study published in the online edition of the Journal of Acquired Immune Deficiency Syndromes suggest.
 
However, men who have difficulty talking about safer sex were significantly more likely to report a willingness to stop using condoms if efficacy was only around 50% - a level similar to that seen in the recent iPrEX study. The study involved HIV-negative gay and other men who have sex with men who reported the use of drugs or alcohol during recent unprotected anal sex with a HIV-positive man or man of unknown HIV status.
 
“Behavioral counseling and other interventions will be especially important to supplement PrEP use and to counterbalance any potential increases in risky behaviors that could result in more HIV transmission due to higher risk behaviors in the setting of PrEP,” comment the investigators.
 
There is considerable excitement about the use of antiretroviral therapy in prevention. Very few HIV transmissions originate in patients who are taking virologically suppressive treatment. In addition, pre-exposure prophylaxis (PrEP) – the treatment of HIV-negative individuals with anti-HIV drugs – has been shown to significantly reduce the risk of infection with HIV.
 
Results of the iPrEX study into the safety and effectiveness of PrEP in gay and other men who have sex with men showed that, overall, it reduced infections by 43%. Much higher levels of efficacy were seen in men with good adherence to their treatment.
 
Discussions are underway about how best to incorporate PrEP into wider HIV prevention campaigns. Some researchers believe that its use should be restricted to individuals who have a very high risk of infection with HIV – for example gay men who have unprotected anal sex when under the influence of drugs or alcohol.
 
Investigators from the US therefore conducted a study involving 645 gay and other men who have sex with men who feel into this category. They were recruited between 2004 and 2008 in Chicago, Los Angeles, New York and San Francisco -  cities with large gay populations and high rates of new HIV infections. The men were asked about their use of PrEP and what levels of efficacy would be needed for them to stop using condoms for insertive or receptive anal sex.
 
Participants were aged between 18 and 67 years, with the majority aunder 35. They were racially diverse and well educated. The vast majority of men identified as gay.
 
Use of PrEP was reported by 15 men. They had used a variety of regimens, but none reported taking Truvada (tenofovir/FTC), the drug investigated in the iPrEX study. Moreover, none of the individuals reported taking therapy for more than a week.
 
Almost three-quarters of men (73%) said that PrEP would need to be always or nearly always effective for them to use it instead of condoms for receptive anal sex. A further 15% of men said that it would need to be effective about 50% of the time, and 12% said they would accept efficacy below 50%.
 
“A considerable proportion of men indicated that PrEP would need to be almost always or always effective to not use a condom for anal intercourse and would likely not rely solely on PrEP for protection,” note the authors.
 
However, given the results of the iPrEX study showing an overall efficacy of 44%, the investigators were especially interested in the characteristics of men who said they would consider PrEP as a replacement for condoms when it stopped approximately 50% of infections.
 
Their analysis showed that these men were significantly (p < 0.001) more likely than the other groups to have difficulty talking about safer sex when under the influence of drugs or alcohol.
 
Overall, men appeared willing to accept lower levels of efficacy for PrEP to be considered a replacement for condoms for insertive anal sex (high efficacy  = 34%; medium efficacy = 49%; low efficacy = 17%).
 
Once again, men in the mid efficacy group were significantly more likely to report difficulty communicating with their partners about safer sex if they had taken drugs or were drunk (p < 0.05).
 
“Difficulty communicating about safer sex while under the influence of alcohol and other substances was consistently found to be an important factor,” write the researchers.
 
They caution that their research was conducted before knowledge of PrEP was widespread among gay men, and that awareness and attitudes to the therapy may have changed after the publication of the iPrEX study results.
 
Nevertheless they comment, “these findings provide guidance on an area that would be important to target in counseling interventions associated with PrEP use.”
 
 
Reference
Koblin BA et al. Condom use decision making in the context of hypothetical pre-exposure prophylaxis efficacy among substance-using men who have sex with men: Project MIX. J Acquir Immune Defic Syndr, online edition: DOI: 10.1097/QAD.10b013e31822b776d2, 2011 (click here for the free abstract).