CROI 2013Using condoms all the time for anal intercourse prevents HIV transmission 70 percent of the time, while using them inconsistently ultimately provides no protection.  Also, only one in six gay men report using condoms all the time for anal sex, according to aidsmap. The Centers for Disease Control and Prevention’s (CDC) analysis of condom efficacy in preventing HIV transmission through anal sex, presented at the 20th Conference on Retroviruses and Opportunistic Infections (CROI) in Atlanta, is only the second of its kind. The 70 percent figure was identical to that of the previous study, conducted in 1989.

The CDC retrospectively analyzed information about condom use and HIV infection from two separate studies of HIV-negative gay men in the United States, including the VAX004 HIV vaccine trial, which was conducted between 1998 and 1999, and EXPLORE, which was a large study of behavioral interventions that ran from 1999 to 2001. Between the two studies, the CDC examined data on 3,490 men who reported unprotected anal sex with an HIV-positive partner, out of a total cohort of 7,366 men. There were 225 HIV transmissions within the two studies. VAX004 had a follow-up time of three years, and EXPLORE had a four-year follow-up.

The analysis found that, among the men having anal sex, those who reported using condoms every time were 67 percent less likely to become HIV positive than those who never used condoms and 64 percent less likely than those who used them only sometimes. There is reason to believe that using condoms correctly as well as consistently had an additional protective measure, due to the fact that the behavioral intervention study EXPLORE saw an 86 percent reduction in HIV transmission as a result of consistent condom use. Between either study there was no statistically significant reduction in HIV transmissions among those who reported inconsistent condom use for anal sex.

Across the cohort, two-thirds of the men reported using condoms all the time during any of the six-months intervals into which each study was divided. However, just 16.4 percent reported consistent use of condoms within all the study intervals. As for men who reported never using condoms, this figure was just 5 percent across the length of both studies, but 40 percent in at least one of the six-month spans.

To read the aidsmap story, click here.

To view the abstract on the CROI web site, click here.

To view a web cast of the presentation, click here.