Serosorting

http://www.aidsmap.com/Serosorting-does-help-prevent-HIV-up-to-a-point/page/2287223Their study found that the strategy of ‘serosorting’, in which men allow themselves to have unprotected sex, but only with partners with the same HIV status as themselves, did have some preventive effect compared to using no prevention strategy at all.

The study presented at CROI looked at four other safer sex strategies as well as serosorting:

• Using condoms during all anal sex with all partners.
• Being monogamous (not always using condoms, but only having one partner, with the same HIV status).
• During unprotected sex, only ever taking the insertive role (being ‘top’).
• 'Seropositioning' - only being 'top' during unprotected sex if partners were HIV positive or of unknown HIV status, and only being 'bottom' if having unprotected sex with partners who were known to be HIV negative.

All these strategies helped to reduce HIV infections, compared with having no strategy at all, but some were more effective than others.

Men who serosorted only had half as many HIV infections as men who did nothing (equal to 51 per cent efficacy). Men who used condoms every time (seropositioning) only had a quarter as many infections (equal to 74 per cent and 75 per cent efficacy respectively). Safer still was only ever being top in unprotected sex, that stopped 85 per cent of infections.

The safest option of all was monogamy. Men who did have unprotected sex, but only in a monogamous relationship with another HIV negative man, had only eight per cent as many HIV infections as men who took no precautions (equal to 92 per cent efficacy).

Some studies have found serosorting in HIV negative men to be effective, others have not. It’s a fallible strategy, because unlike people who know they are HIV positive, HIV negative people can only be sure of their HIV status up to the first risky encounter after a negative HIV test. Research indicates that a fair proportion of people in high-risk communities who think they are HIV negative actually have HIV, and that a lot of men who ‘know’ their partner’s HIV status have in fact tried to guess it.

The 74 per cent efficacy of using condoms every time is backed up by other studies of condom efficacy in anal sex. However, it’s notable that a couple of strategies that included condomless sex, but only in relatively safe circumstances, were in fact safer than attempting to use condoms 100 per cent of the time regardless of partner.