How do we stop the hyperepidemic in gay men?
A number of presentations at the 19th International AIDS Conference explored the ‘hyperepidemic’ of HIV amongst men who have sex with men, and especially black MSM.
A paper presented by Gregorio Millet showed that, at least in the USA, the extremely high incidence and prevalence of HIV in this group is not driven by higher levels of unsafe sex. Instead, very high prevalence, the ease with which HIV is transmitted during anal sex, and the fact that black men (and some other subpopulations of gay men) have sex within small and multiply-connected networks have created a situation in which HIV is hard to avoid.
Given this, what prevention methods would work in gay men? The one that has been talked about most keenly and which continued to generate a great deal of data and debate at Washington was pre-exposure prophylaxis (PrEP) – taking antiretrovirals (ARVs) to prevent, rather than treat, HIV.
Will PrEP work?
The subject was already being discussed before the main conference in the satellite ‘preconference’ organised by the Global Forum for Men who have Sex with Men and HIV (MSMGF) the day before the main conference opened.
Bob Grant, Principal Investigator of iPrEx, the proof-of-concept study of PrEP in gay men, told the preconference that in his view it was misleading to quote the 42% efficacy observed as if this was the highest achievable in gay men. Drug level studies in iPrEx (and in the Partners PrEP study in different-status heterosexual couples) had shown that the reduction in the risk of HIV infection in people with detectable drug in their blood – implying adequate adherence levels – was in the order of 90-92%, and that in iPrEx, in the relatively few subjects at US sites, drug had been detectable in 94% of samples.
In addition, in iPrEx as a whole, adherence had correlated with risk: participants who had unprotected receptive anal sex had higher adherence to PrEP than ones who didn’t and PrEP efficacy was somewhat higher in this group as a result (53%). For Grant, this showed that PrEP is likely to be used by those who need it most. He recommended that use of PrEP should be guided by the person’s request to have it more than the physician’s judgement that they need it, and that PrEP and other biomedical prevention interventions are likely to work better in a non-judgmental atmosphere where stigmatising language is avoided.
In the main conference, in a symposium that discussed papers published in a special issue of The Lancet that focused on men who have sex with men (MSM), Patrick Sullivan of Emory University, Atlanta presented a model of the likely reduction in HIV infections in men who have sex with men (MSM) in four different countries (Kenya, the US, Peru and India) using three different prevention programmes: one with an intensified emphasis on condom use as its primary ingredient, one focusing on earlier treatment for MSM with HIV, and one adding PrEP to existing prevention programmes.
The base model used assumed one of the following three scenarios:
· Uptake of PrEP in gay men needing it at rates ranging from 20% to 80% and also at various adherence rates, ranging from 50% to 90%;
· an increase, ranging from 20% to 80%, in the proportion of men taking ARVs with CD4 counts above 200 cells/mm3 or (in the USA) 350 cells/mm3 (these being the ART thresholds at the time the model was done);
· an increase in condom use over baseline from 10% to 40%.
His model found that PrEP, under these scenarios, would be slightly more effective than condom promotion in all countries other than India, though only by a couple of percentage points in terms of the proportion of HIV infections averted that would otherwise have happened. For instance this proportion would be about 23% with 40% PrEP uptake, and about 20% with a 20% increase in condom use.
In all countries but Kenya, the model suggested that earlier treatment would have less effect than the other two interventions. The reason condoms would be more effective in India is because usage rates in MSM in that country are, at least in studies, higher, so a percentage rise in condom use would involve a greater number of extra condoms being used and have a greater effect on the remaining HIV transmissions. Conversely, in a country like Kenya where people currently start ART later than elsewhere, the consequence of starting it early is greater.
Sullivan said his model predicted that, using the most realistic scenarios, 25% of infections could be averted over the next ten years in MSM using a combination of these methods. However this would happen only if the criminalisation of male/male sex, threats and violence against MSM, lack of understanding and training among healthcare workers, and barriers against implementation research were addressed.
In a poster session, Kate Mitchell of the London School of Hygiene and Tropical Medicine found that the effectiveness of PrEP would vary widely according to how carefully gay men were targeted for it, using India as an example.
India has had quite a segregated MSM population historically, with feminine, gay-identified ‘kothi’ men who take the receptive role in sex and non-gay-identified ‘panthis’ who take the insertive role tending to stay in their separate populations (this means panthis, who do not identify as gay, are harder to reach). A third identity as ‘double decker’ or ‘dupli’, i.e. versatile, has grown up amongst urbanised gay men more recently.
In her model a PrEP intervention targeted at kothis or duplis, in which the intervention was 42% effective and was taken up by 60% of targeted men, would prevent 25-30% of HIV infections, whereas if PrEP were targeted at panthis, or selectively used by them, the result would be only a 5%-10% reduction in HIV infections.
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