A recent estimate from the CDC says that condoms, when used 100% of the time, are 91% effective at preventing the spread of HIV through anal sex.
The latest figure comes from analysis of four major studies on the topic, reports AIDSMap. Notably, the percentage is much closer to the efficacy of condoms for opposite-sex couples—and much higher than previous estimates for gay men. In both a 1989 and a 2014 study, researchers found that condoms were only effective at preventing HIV transmission 7/10 times.
The CDC believes the higher figure in its most recent report could be explained by its research methods: Instead of gauging condom efficacy per sex act, the agency drew conclusions per participants’ number of partners. (In incidents where there are more than one sex act between a couple, the risk of contracting HIV tends to decrease over time.)
But more partners doesn’t necessarily mean a higher risk of infection. Interestingly, the CDC found that for men who always use condoms, the per-partner risk actually decreases the more partners they have.
There are a few notable gaps in the CDC’s report. For one thing, all of the data analyzed by the CDC were published after the advent of pre-exposure prophylaxis, or PrEP, first approved by the FDA in 2012 for regular use to prevent HIV transmission.
For another, participants in the studies had to use condoms 100% of the time, something many queer couples simply don’t do, especially in the age of PrEP.