PrEP to curb new infections among MSM

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Antiretroviral therapy (ART) taken as pre-exposure prophylaxis (PrEP) could help dramatically reduce the new HIV infection rate among men who have sex with men (MSM), according to a new study.

Research led by the London School of Hygiene & Tropical Medicine examined the effectiveness of PrEP used alongside regular HIV testing and early treatment. They found that offering this three-pronged approach to just a quarter of MSM at high risk of contracting HIV could prevent around 7,400 new HIV infections (44% of total incidence) in the UK by 2020.

PrEP is an HIV prevention strategy in which people at high risk of becoming exposed to HIV take antiretroviral drugs to reduce their chance of becoming infected. The medication helps to prevent the virus from establishing itself and multiplying in the body.

In this study a mathematical model was fitted with behavioural and surveillance data to evaluate the ability of various HIV prevention measures including expansion of HIV testing, test-and-treat programmes, PrEP, and sexual behavioural changes, to prevent HIV infections in MSM (aged 15 to 64 years old) in the UK between 2014 and 2020. If the status quo is maintained, the researchers predict 16,955 new HIV infections in MSM between 2014 and 2020.

The researchers estimate that even when targeted only at high-risk men, PrEP was more effective than all other individual measures aimed at the entire UK MSM population, preventing 59% of new infections (9,955). However, they predict that the greatest number of infections would be prevented by a ‘practical combined prevention programme’ that includes PrEP alongside yearly HIV testing for HIV-negative men and immediate ART for HIV-positive men.

Dr Narat Punyacharoensin who conducted the research while at the London School of Hygiene & Tropical Medicine, said: “Current prevention efforts in the UK that focus on correct and consistent condom use and regular HIV testing have been falling short. HIV rates among men who have sex with men remain high with around 2,800 men who have sex with men becoming infected with HIV in 2014, and the trend shows no sign of abating. Our results show that pre-exposure prophylaxis offers a major opportunity to curb new infections and could help reverse the HIV epidemic among men who have sex with men in the UK.”

One of the main concerns about PrEP is whether men who know they are protected by prophylaxis will compensate for this by increasing their sexual risk-taking, for example by increasing their levels of unprotected sex (risk compensation). In this study, risk-compensation analyses indicate that even a substantial increase in unprotected anal intercourse and sexual partners is unlikely to completely counteract the strong HIV prevention benefit of prophylaxis.

Professor Noel Gill, head of Public Health England’s HIV and STI department and a co-author, said: “The findings imply that a pre-exposure prophylaxis programme could be an important addition to current efforts to prevent HIV transmission in England. Public Health England has provided much evidence to NHS England to help inform their decision analysis process. This evidence includes studies on the cost-effectiveness, the budgetary impact, and public health impact of a possible publically funded HIV pre-exposure prophylaxis policy.”

Summary
Background
HIV transmission in men who have sex with men (MSM) in the UK has shown no sign of decreasing in the past decade. Additional prevention measures are needed. We aimed to estimate the effect of various potential interventions implemented individually and in combination on prevention of HIV infection.
Methods
We extended a deterministic partnership-based mathematical model for HIV transmission, informed by detailed behavioural and surveillance data, to assess the effect of seven different HIV interventions implemented in MSM (aged 15–64 years) in the UK during 2014–20, including increasing rates of HIV testing, test-and-treat programmes, pre-exposure prophylaxis (PrEP), and sexual behavioural changes. We did sensitivity analyses on risk compensation.
Findings
We predicted a baseline of 16 955 new infections (IQR 13 156–21 669) in MSM in the UK during 2014–20. At a coverage of ≤50%, testing twice a year outperformed all other interventions. Of all intervention combinations, only the combined effect of test and treat and annual HIV testing (61•8%, IQR 47•2–81•8, of total incidence) was greater than the sum of effects of the two interventions individually (32•6%, 23•7–46•0, and 23•9%, 16•5–33•3, respectively). Simultaneous PrEP, expansion of HIV testing, and initiation of test-and-treat programme in 25% of high-activity MSM could save 7399 (IQR 5587–9813) UK MSM from HIV infection (43•6%, IQR 32•9–57•9, of total incidence). An increase in unsafe sex or sexual partners to 50% or more could substantially reduce the effect of interventions, but is unlikely to negate the prevention benefit completely.
Interpretation
PrEP could prevent a large number of new HIV infections if other key strategies including HIV testing and treatment are simultaneously expanded and improved. Without PrEP, HIV incidence in MSM in the UK is unlikely to decrease substantially by the end of this decade.

London School of Hygiene & Tropical Medicine material
The Lancet HIV article summary


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