Effectiveness of HIV Treatment as Prevention Among MSM
Effectiveness of HIV Treatment as Prevention Among MSM
Objectives In the UK, free HIV care is provided through dedicated HIV clinics. Using the national cohort of men who have sex with men (MSM) with diagnosed HIV infection and estimates of the number of undiagnosed men, we assessed whether high retention in HIV care and treatment coverage is sufficient to reduce HIV transmission.
Methods Antiretroviral therapy (ART) uptake and viral load distribution among diagnosed men were analysed by treatment status and CD4 count for the period between 2006 and 2010. A multi-parameter evidence synthesis (MPES) method was used to estimate the size of the undiagnosed population. The viral load distribution among newly diagnosed untreated men was applied to the undiagnosed population. Infectivity was defined as a viral load > 1500 HIV-1 RNA copies/mL.
Results Between 2006 and 2010, ART coverage among all HIV-infected MSM (diagnosed and undiagnosed) increased from 49 to 60%, while the proportion of infectious men fell from 47 to 35%. Over the same period, the number of all HIV-infected MSM increased from 30 000 to 40 100 and the number of infectious MSM remained stable at 14 000. Of the 14 000 infectious MSM in 2010, 62% were undiagnosed, 33% were diagnosed but untreated, and 5% received ART. Extending ART to all diagnosed HIV-infected MSM with CD4 counts < 500 cells/μL in 2010 would have reduced the overall proportion of infectious men from 35 to 29% and halving the proportion who were undiagnosed would further have reduced this to 21%.
Conclusions High ART coverage in the UK has reduced the infectivity of the HIV-diagnosed population. However, the effectiveness of treatment as prevention will be limited unless the undiagnosed population is reduced through frequent HIV testing and consistent condom use.
The demonstration that prevention of HIV transmission was possible through antiretroviral therapy (ART) was described as 'a defining moment for HIV control' in mid-2011 and the 'breakthrough of the year' for scientific research in December 2011. ART has been shown to be highly efficacious at preventing transmission from HIV-infected to HIV-negative heterosexual partners, providing that the HIV-positive partner adheres to treatment so that their viral load becomes undetectable.
While the benefit of HIV treatment for HIV-negative heterosexuals in HIV-serodiscordant relationships has been demonstrated, there is uncertainty surrounding the clinical benefits of 'early' ART (starting ART before the CD4 count reaches 500 cells/μL) for HIV-positive individuals. The START trial is designed to identify the impact of early ART initiation among the HIV-diagnosed population on the development of AIDS-related and non-AIDS-related illnesses. Additional measurable outcomes include adherence, the development of antiretroviral resistance and patient satisfaction. This work will directly inform future national and international treatment policies.
However, even if early treatment for the diagnosed HIV-positive population is found to be clinically beneficial, there is continued uncertainty about a population-level prevention effect that could be achieved if ART coverage were high enough to reduce 'community viral load' (CVL). This challenge appears to be greatest in the USA where, in 2008, only 63% of HIV-infected men who have sex with men (MSM) were established in care following HIV diagnosis and 48% retained in care year on year. Consequently, it was estimated that only 19% of the 1.1 million adults living with HIV in the USA had an undetectable viral load, reducing their risk of transmission. It is suggested that if engagement and retention in HIV care following diagnosis were improved so that the 76% of those requiring ART in the USA received it, then the CVL might be reduced below the level needed to sustain transmission.
The UK is well placed to explore the relationship between ART coverage and transmission. HIV is endemic in MSM, with an estimated prevalence of 9% in London and 3% elsewhere. Provision through the National Health Service (NHS) has enabled free, universal access to HIV testing, treatment and specialized care services. Consequently, in 2010, 98% of all HIV-positive patients were established in care 3 months after diagnosis and at least 95% of all patients were retained in care year on year. Treatment coverage was high, with over 90% of MSM diagnosed and meeting treatment criteria receiving ART in 2010.
British HIV Association (BHIVA) treatment guidelines have broadly mirrored US guidelines; in 2008 both recommended ART be initiated before CD4 counts fell below 350 cells/μL. In 2009, US guidelines recommended that treatment began at < 500 cells/μL and, in 2012, these were further updated to consider ART for all HIV-infected individuals, partially in response to the demonstration of the prevention effect of treatment. A similar change is now indicated in the UK for people who wish to protect their negative partners from infection and the World Health Organisation has recently recommended treatment to start at < 500 cells/mm to prevent transmission.
We used comprehensive HIV surveillance data and estimates of undiagnosed infection to describe the viral load distribution among MSM living with HIV in the UK and to estimate the proportion of men who are at risk of passing on their HIV infection by treatment and CD4 status. We define 'infectiousness' as a viral load > 1500 HIV-1 RNA copies/mL. The potential for a population-level reduction in HIV transmission through treatment as prevention among MSM is discussed.
Abstract and Introduction
Abstract
Objectives In the UK, free HIV care is provided through dedicated HIV clinics. Using the national cohort of men who have sex with men (MSM) with diagnosed HIV infection and estimates of the number of undiagnosed men, we assessed whether high retention in HIV care and treatment coverage is sufficient to reduce HIV transmission.
Methods Antiretroviral therapy (ART) uptake and viral load distribution among diagnosed men were analysed by treatment status and CD4 count for the period between 2006 and 2010. A multi-parameter evidence synthesis (MPES) method was used to estimate the size of the undiagnosed population. The viral load distribution among newly diagnosed untreated men was applied to the undiagnosed population. Infectivity was defined as a viral load > 1500 HIV-1 RNA copies/mL.
Results Between 2006 and 2010, ART coverage among all HIV-infected MSM (diagnosed and undiagnosed) increased from 49 to 60%, while the proportion of infectious men fell from 47 to 35%. Over the same period, the number of all HIV-infected MSM increased from 30 000 to 40 100 and the number of infectious MSM remained stable at 14 000. Of the 14 000 infectious MSM in 2010, 62% were undiagnosed, 33% were diagnosed but untreated, and 5% received ART. Extending ART to all diagnosed HIV-infected MSM with CD4 counts < 500 cells/μL in 2010 would have reduced the overall proportion of infectious men from 35 to 29% and halving the proportion who were undiagnosed would further have reduced this to 21%.
Conclusions High ART coverage in the UK has reduced the infectivity of the HIV-diagnosed population. However, the effectiveness of treatment as prevention will be limited unless the undiagnosed population is reduced through frequent HIV testing and consistent condom use.
Introduction
The demonstration that prevention of HIV transmission was possible through antiretroviral therapy (ART) was described as 'a defining moment for HIV control' in mid-2011 and the 'breakthrough of the year' for scientific research in December 2011. ART has been shown to be highly efficacious at preventing transmission from HIV-infected to HIV-negative heterosexual partners, providing that the HIV-positive partner adheres to treatment so that their viral load becomes undetectable.
While the benefit of HIV treatment for HIV-negative heterosexuals in HIV-serodiscordant relationships has been demonstrated, there is uncertainty surrounding the clinical benefits of 'early' ART (starting ART before the CD4 count reaches 500 cells/μL) for HIV-positive individuals. The START trial is designed to identify the impact of early ART initiation among the HIV-diagnosed population on the development of AIDS-related and non-AIDS-related illnesses. Additional measurable outcomes include adherence, the development of antiretroviral resistance and patient satisfaction. This work will directly inform future national and international treatment policies.
However, even if early treatment for the diagnosed HIV-positive population is found to be clinically beneficial, there is continued uncertainty about a population-level prevention effect that could be achieved if ART coverage were high enough to reduce 'community viral load' (CVL). This challenge appears to be greatest in the USA where, in 2008, only 63% of HIV-infected men who have sex with men (MSM) were established in care following HIV diagnosis and 48% retained in care year on year. Consequently, it was estimated that only 19% of the 1.1 million adults living with HIV in the USA had an undetectable viral load, reducing their risk of transmission. It is suggested that if engagement and retention in HIV care following diagnosis were improved so that the 76% of those requiring ART in the USA received it, then the CVL might be reduced below the level needed to sustain transmission.
The UK is well placed to explore the relationship between ART coverage and transmission. HIV is endemic in MSM, with an estimated prevalence of 9% in London and 3% elsewhere. Provision through the National Health Service (NHS) has enabled free, universal access to HIV testing, treatment and specialized care services. Consequently, in 2010, 98% of all HIV-positive patients were established in care 3 months after diagnosis and at least 95% of all patients were retained in care year on year. Treatment coverage was high, with over 90% of MSM diagnosed and meeting treatment criteria receiving ART in 2010.
British HIV Association (BHIVA) treatment guidelines have broadly mirrored US guidelines; in 2008 both recommended ART be initiated before CD4 counts fell below 350 cells/μL. In 2009, US guidelines recommended that treatment began at < 500 cells/μL and, in 2012, these were further updated to consider ART for all HIV-infected individuals, partially in response to the demonstration of the prevention effect of treatment. A similar change is now indicated in the UK for people who wish to protect their negative partners from infection and the World Health Organisation has recently recommended treatment to start at < 500 cells/mm to prevent transmission.
We used comprehensive HIV surveillance data and estimates of undiagnosed infection to describe the viral load distribution among MSM living with HIV in the UK and to estimate the proportion of men who are at risk of passing on their HIV infection by treatment and CD4 status. We define 'infectiousness' as a viral load > 1500 HIV-1 RNA copies/mL. The potential for a population-level reduction in HIV transmission through treatment as prevention among MSM is discussed.