TasP suppresses new HIV infections among gay and bisexual men in Australia

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HIV treatment as prevention, as measured in community-level viral suppression, was strongly associated with a large drop in the number of new HIV infections among gay and bisexual men in Australia, even before PrEP was available. This study was presented by Dr Denton Callander from the University of New South Wales at the Conference on Retroviruses and Opportunistic Infections (CROI 2020).

Despite the clear benefits of treatment as prevention (or Undetectable = Untransmittable, U=U) at the individual level, no large-scale studies have yet evaluated the community-level effects of treatment as prevention (TasP) on direct measures of HIV incidence among gay and bisexual men. Previous research has indicated a disconnect between the benefits of TasP/U=U at the individual and population levels.

Data for this study came from the Australian ACCESS database: an existing large surveillance system that collects anonymous data on sexually transmitted infections in gay and bisexual men. The study took place in Australia’s two most populous states, New South Wales and Victoria from 2012 to 2017. Data was taken from 67 sites including sexual health clinics, hospitals, general practices and community testing sites.

The authors demonstrated that between 2012 and 2017, there had been major increases in treatment uptake for HIV-positive gay and bisexual men, with subsequent drops in viraemia. This decreased level of community viraemia was strongly associated with a reduction in the number of men diagnosed HIV positive in this period. A significant point is that this relationship existed prior to the introduction of PrEP in these Australian states.

“This provides at least one kind of evidence in support of TasP as a public health strategy,” Callander concluded. “It suggests that Australia’s investment in TasP and treatment generally seems to really have had a public health payoff.”

Abstract
Considerable public health resources have been dedicated to implementing HIV treatment-as-prevention in an effort to reduce new infections. Although promising, no large-scale studies have yet evaluated the community-level impact of treatment-as-prevention on direct measures of HIV incidence among gay and bisexual men (GBM). This study assessed the temporal relationship between community viremia and HIV incidence among GBM living in New South Wales and Victoria, Australias most populous states.

For 2012-2017, we established a longitudinal cohort of HIV-positive (n=12,200) and HIV-negative (n=45,719) GBM using data from a targeted sentinel surveillance system of 49 sexual health clinics, general practices, community HIV-testing sites and hospitals. Among GBM with diagnosed HIV, annual prevalence of viremia was calculated for each patient’s last viral load test of a calendar year (≥200 RNA copies/mm3 ) while mathematical modelling was used to estimate the proportion of HIV-positive GBM living with undiagnosed HIV infection (assuming 100% viremia); these outcomes were combined to estimate ‘community viremia’. A correlation coefficient was calculated to assess the temporal relationship between community viremia and HIV incidence, which was directly measured among HIV-negative sentinel surveillance patients using the repeat testing method. To account for the introduction of HIV pre-exposure prophylaxis (PrEP) in 2016, the analysis was repeated for the 2012-2015 period only.
HIV viremia among diagnosed GBM decreased from 27.9% in 2012 to 3.7% in 2017 (p<0.001) while the proportion living with undiagnosed HIV decreased from 10.0% to 8.4% (p=0.01). As shown in Figure 1, annual community prevalence of HIV viremia decreased from 28.6% in 2012 to 12.8% in 2017 (p<0.001) while HIV incidence decreased from 0.88/100 person years in 2012 to 0.22/100 person years in 2017 (p<0.001). The correlation coefficient between annual community prevalence of viremia and HIV incidence from 2012 to 2017 was 0.94 (p<0.001) and for 2012 to 2015 was 0.90 (p<0.001).
Decreasing community viremia among GBM was strongly associated with decreasing HIV incidence, including before the implementation of PrEP. Our findings justify the significant investment in HIV treatment initiatives, highlighting that these should be sustained as key elements of HIV prevention.

Authors
Denton J Callander, Mark Stoové, Hamish McManus, Andrew Carr, Richard Gray, Jennifer Hoy, Basil Donovan, Margaret Hellard, Andrew E Grulich

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CROI 2020

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