Increased HIV Incidence in Men Who Have Sex with Men Despite High Levels of ART-Induced Viral Suppression: Analysis of an Extensively Documented Epidemic

Abstract

BackgroundThere is interest in expanding ART to prevent HIV transmission, but in the group with the highest levels of ART use, men-who-have-sex-with-men (MSM), numbers of new infections diagnosed each year have not decreased as ARTcoverage has increased for reasons which remain unclear.MethodsWe analysed data on the HIV-epidemic in MSM in the UK from a range of sources using an individual-based simulation model. Model runs using parameter sets found to result in good model fit were used to infer changes in HIV-incidence and risk behaviour.ResultsHIV-incidence has increased (estimated mean incidence 0.30/100 person-years 1990–1997, 0.45/100 py 1998–2010), associated with a modest (26%) rise in condomless sex. We also explored counter-factual scenarios: had ART not been introduced, but the rise in condomless sex had still occurred, then incidence 2006–2010 was 68% higher; a policy of ART initiation in all diagnosed with HIV from 2001 resulted in 32% lower incidence; had levels of HIV testing been higher (68% tested/year instead of 25%) incidence was 25% lower; a combination of higher testing and ART at diagnosis resulted in 62% lower incidence; cessation of all condom use in 2000 resulted in a 424% increase in incidence. In 2010, we estimate that undiagnosed men, the majority in primary infection, accounted for 82% of new infections.ConclusionA rise in HIV-incidence has occurred in MSM in the UK despite an only modest increase in levels of condomless sex and high coverage of ART. ART has almost certainly exerted a limiting effect on incidence. Much higher rates of HIV testing combined with initiation of ART at diagnosis would be likely to lead to substantial reductions in HIV incidence. Increased condom use should be promoted to avoid the erosion of the benefits of ART and to prevent other serious sexually transmitted infections.

HIV treatment as prevention among men who have sex with men in the UK: is transmission controlled by universal access to HIV treatment and care?

“…However, extended work on the MPES model has indicated that the level of undiagnosed HIV infections was stable between 2001 and 2008 in England and Wales [22]. Furthermore, the method has been found to be robust [22] and its results have been corroborated with other estimates of the size of the undiagnosed MSM population [22,30,31].…”

“…However, extended work on the MPES model has indicated that the level of undiagnosed HIV infections was stable between 2008 in England and Wales [22]. Furthermore, the method has been found to be robust [22] and its results have been corroborated with other estimates of the size of the undiagnosed MSM population [22,30,31].The threshold for infectivity was defined as a viral load > 1500 copies/mL for two reasons. Firstly, no sexual transmissions were found to occur below this level in an observational study of serodiscordant heterosexuals [19].…”

Implications for a policy of initiating antiretroviral therapy in people diagnosed with human immunodeficiency virus: the CAPRA research programme

“…A third consideration is that a high proportion of new infections come from men who are not yet diagnosed, and in many cases men who have only just been infected. [12][13][14] This might seem to limit the influence that ART can have in reducing new HIV infections in MSM. We should also consider how high the rate of HIV testing is, and how rapidly those who are infected become diagnosed and linked to care.…”

“…The work was reported in two papers. 1,14 The first concentrated on understanding influences on the epidemic up to 2012 and described the structure and calibration of the model of HIV transmission, progression and the effect of ART that was developed for this. The model was then used to help us understand the relative influences of sexual risk behaviour change, rates of HIV testing and ART-induced virological suppression on HIV infection incidence up to 2012.…”

“…1 In the second paper we used the model to project future HIV infection incidence and other outcomes over the next 20 years, along with an economic analysis. 14 In the model we reconstruct sexual risk behaviour, HIV transmission, progression and the effect of ART for the population of MSM in the UK from 1980 to 2010 using an individual-based stochastic computer simulation model, which captures the key underlying mechanisms that determine these processes (model adapted from that used in Phillips et al, 58 itself developed from earlier versions [59][60][61] ). We were able to calibrate the model quite closely to a range of data.…”