Consistent condom use during anal sex prevents 70% of HIV infections among men who have sex with men (MSM) in the U.S., according to an analysis by Centers for Disease Control and Prevention (CDC) researchers that was published ahead of print on Dec. 2 in the Journal of Acquired Immune Deficiency Syndromes.
In "Condom Effectiveness for HIV Prevention by Consistency of Use among Men Who Have Sex with Men (MSM) in the U.S.," data from two large studies were examined to determine the effectiveness of condoms in reducing HIV transmission among MSM who reported "always" using condoms during anal sex, compared with those who reported "sometimes" or "never" using condoms.
In the analysis, which had been presented earlier at the 2013 Conference on Retroviruses and Opportunistic Infections (CROI), the CDC researchers found that "among MSM reporting any anal sex with an HIV-positive male partner, we found 70% effectiveness with reported consistent condom use (compared to never use) and no significant protection when comparing sometimes use to never use."
The study used existing data sets from two HIV prevention trials that enrolled HIV-uninfected MSM in the U.S. Researchers asked participants about their sexual behaviors and conducted HIV testing every six months over a number of years.
Notably, the study observed low rates of consistent condom use. Only 16% of participants reported "always" using condoms during anal sex with male partners (of any HIV status) throughout the entire study period, despite having received sustained behavioral interventions.
"Our findings of strong but partial effectiveness for consistent condom use, minimal effectiveness for inconsistent condom use, and low rates of consistent condom use over 1-2 years, even among persons receiving high quality risk-reduction counseling, may contribute to a better understanding of the persistent rates of HIV infection among MSM in the U.S., despite current levels of condom use promotion and provision," the study concluded.
Researchers did not explain how some participants contracted HIV despite reporting they "always" used condoms. However, they said self-reports of condom use were not validated, so it is possible some participants failed to report instances of condomless sex. Participants who reported injecting drugs before or during the trial period were excluded from the study.
While MSM represent approximately 2% of the U.S. adult population, researchers explained they accounted for 62% of all newly diagnosed HIV infections.
Yet few studies have looked at the effectiveness of condom use among this population. The most widely used estimate of condom effectiveness (80%) was based on studies among heterosexual people with HIV-positive partners.
"Given that the proportion of new HIV infections in the U.S. annually is greatest for MSM, it is important to have robust and accurate estimates of the effectiveness of condoms and other prevention methods that are specific to this population," the researchers explained.
They said the difference between heterosexual and MSM estimates was not statistically significant, but recommended using the new MSM estimate of 70% for discussions and models involving anal sex among MSM, rather than continuing to use the heterosexual estimate of 80%.
"From a public health perspective, these data suggest the need to further intensify efforts to educate HIV-uninfected MSM and improve their ability to accurately assess both their risk of HIV acquisition and the effectiveness of their current use of condoms (consistently or inconsistently) during anal sex," the study authors wrote.
"These data also suggest a need to provide access to additional highly effective HIV prevention tools and strategies, including more frequent HIV testing (including testing as couples) and daily oral antiretroviral pre-exposure prophylaxis (PrEP) when indicated," they added.
Katherine Moriarty is a consultant and freelance writer, based in Vancouver. She has 10 years of experience in the intersecting fields of public health and community development, with a focus on bloodborne virus policy and programming.