Recent reports on the effectiveness of serosorting, compared to other HIV risk reduction measures, have touched off a lively discussion in the Federal AIDS Policy Project (FAPP): does serosorting work, and when does it work? In serosorting, people have sex only with partners who have the same HIV status that they do -- positives with positives, negatives with negatives. And because they have the same status, they feel free to have sex without condoms.
Does it work? A 2008 study found it does -- but only up to a point. "[Serosorting] offers some protection against HIV," the study's authors wrote, "but a large proportion of persons with newly diagnosed HIV report UAI with partners they believe to be HIV uninfected as their highest risk sexual behavior. We also observed what may be a decline in the protective efficacy of serosorting over time."
We wonder whether the effectiveness of serosorting in a population can be predicted on the basis of just two variables: what percentage of the population has untreated HIV, and what percentage of that subset does not know it is infected? Where those two percentages are low, serosorting can be effective -- although possibly still less effective than consistent condom use. Where those two percentages are high, the risk of unintended unprotected sex between one partner who is negative and one who is positive and untreated is also high, and serosorting is not likely to be effective.
Perhaps, then, serosorting can be somewhat effective is reducing HIV transmission risk in settings where almost everyone gets tested, and almost everyone who tests positive gets treatment. That sounds a lot more like Massachusetts than like some states in the Deep South. The purpose of the Affordable Care Act (ACA) is to help the rest of the country look more like Massachusetts. We want to end this epidemic. Serosorting may have a role to play in that -- but only if we implement ACA.