Two years ago, the Opposites
Attract study
found no transmissions between 343 regular gay couples of
differing HIV status where the HIV-positive partner had a viral load under 200
copies/ml, the negative partner was not taking pre-exposure prophylaxis (PrEP), and they did not use a condom. In doing so, alongside the PARTNER
, it provided the evidence that people with HIV who had an
undetectable viral load were not infectious or, to quote the slogan that has
become a global brand, undetectable
= untransmittable (U=U)

A new analysis has now delved deeper into the actual sex and
prevention behaviour of those who took part in Opposites Attract and found that
couples were by no means just relying on the positive partner’s undetectable
viral load to avoid the negative partner becoming infected. Some used different strategies altogether, while others combined strategies in a
‘belt-and-braces’ fashion.

This new study looks at couple’s sexual prevention behaviours at all time points in the study. The previous analysis, of whether there was any risk of transmission by the HIV-positive partner if he had an undetectable viral load, excluded all sex acts that were covered by condoms or PrEP. In fact, a high proportion of couples continued to use condoms all or some of the time and a third of the negative
partners took PrEP during at least part of the study.

There was also high usage
of ‘seropositioning’ (the HIV-negative partner taking the insertive role and the positive partner the receptive role), which also reduces the risk of HIV, but because some risk still remains, times when couples practised seropositioning were not excluded.

Opposites Attract started in Australia but later extended to
sites in Brazil and Thailand, and there were interesting differences between
the HIV prevention choices in the different countries. In
Thailand in particular, a high proportion of the HIV-positive partners had not
started antiretroviral therapy (ART) when they entered the study, though nearly
all had by its end. Viral load tests are conducted less
often there, and this may explain why Thai participants were more likely to use
condoms or PrEP, alone or in combination, as their main protective behaviour.

The new analysis provides an interesting snapshot of how gay men’s sexual risk and HIV prevention behaviour was changing during a period
of transition when universal ART on diagnosis was
becoming established and PrEP was becoming more available, but the awareness of
them both was perhaps spreading more slowly.