PrEP in Hong Kong - less targeting is more effective

26 September 2018

Surprising research from Hong Kong reveals that providing PrEP to a third of gay men averts more new infections than only targeting gay men most at risk.

A pharmacy in Hong Kong

A modelling study and cost-effectiveness analysis from Hong Kong finds that in settings with relatively low HIV incidence, providing pre-exposure prophylaxis (PrEP) for men who have sex with men, regardless of their HIV risk, could be more effective at controlling HIV than a targeted approach.

The study, published in Scientific Reports, found that giving PrEP to 30% of men who have sex with men in Hong Kong, regardless of how at risk they are of acquiring HIV, would avert more new infections than prioritising only those with the highest risk of infection. This was combined with a ‘test-and-treat’ strategy, where everybody testing positive for HIV is immediately initiated on antiretroviral treatment.  

To date, numerous PrEP modelling studies relating to men who have sex with men have been conducted around the world. However, only a few have been reported from Asia, and these have been carried out in countries such as India and South Korea where heterosexual transmission drives HIV.

In Hong Kong, HIV predominantly affects men who have sex with men and despite relatively low incidence, new infections are increasing (from 170 in 2010 to 464 in 2015). As of 2015, the total number of HIV-positive men who have sex with men stood at 3,151, equating to 5% prevalence. As treatment coverage and viral load suppression rates are already relatively high among this population due to successful test-and-treat strategies, PrEP could offer an effective new way to reverse the rising infection rate.

The World Health Organization (WHO) currently recommends prioritising PrEP for populations at substantial risk of HIV. In settings such as Hong Kong, where the annual number of new HIV infections is relatively low and only a small proportion of men who have sex with men engage in high-risk behaviours, the task of identifying which men who have sex with men are high-risk is challenging.

The study is based on data from all three publically owned HIV clinics in Hong Kong, which accounts for 96% of all HIV-positive men who have sex with men up to 2012, and local behavioural data. Researchers classified people with eight or fewer partners a year as being low risk, and those with nine or more as high risk. In total, 57% of cases included in the research were classified as low-risk.

The findings suggest that, without PrEP, HIV incidence (per 100 person-years) in Hong Kong is likely to increase from 1.1 to 1.6 between 2011 and 2021. However, the model suggests that the implementation of PrEP between 2017 and 2021 would avert between 3% and 63% of new infections. The wide range here will depend on PrEP coverage, adherence levels and the effectiveness of implementing mixed interventions.

Importantly, researchers found that offering PrEP to all gay men who have unprotected sex, regardless of their number of partners or other behaviours, would avert more new infections than offering PrEP exclusively to high-risk men.

Researchers also examined the cost effectiveness of introducing non-targeted PrEP in Hong Kong, given its low HIV incidence. They found that PrEP’s high cost, which in 2017 stood at US $7,880 per person per year, meant this approach is not currently cost-effective. However, if a 93% reduction in the cost of PrEP were to occur in line with generic versions, researchers found that offering PrEP to 30% of men who have sex with men would offer better value for money than only targeting those with the highest risk – as more infections would be averted.

These findings are likely to be applicable in places with similarly low HIV incidence but where men who have sex with men face high HIV prevalence, particularly in Asia. They highlight the importance of approaching PrEP implementation in ways that respond to the specifics of the HIV epidemic within that context.

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Written by Hester Phillips