Declines in condom use while on PrEP does not increase HIV risk in sex workers

02 November 2017

PrEP for sex workers in South Africa can be a success for HIV prevention, as long as high levels of adherence are maintained.

A woman in Cape Town

Female sex workers who report low levels of condom use (defined as only using condoms 65% or less of the time) and use pre-exposure prophylaxis (PrEP), would not increase their HIV risk if condom use were to decline still further.   

The research, conducted by the London School of Hygiene & Tropical Medicine, looked at the effect PrEP would have on HIV risk among female sex workers in Johannesburg, among whom HIV prevalence is high (72%).

Comparing HIV-risk estimates before and after the introduction of PrEP for sex workers in the country, they sought to find the maximum tolerated reductions in condom use with regular partners and clients before it would affect HIV risk.

They found that the effectiveness of PrEP as an intervention for this group largely depends on individuals’ ability to maintain high levels of adherence to PrEP so that its average effectiveness across the group exceeds the risk reduction effectiveness of condom use.

In scenarios where PrEP was at least 75% effective (based on how well they adhere to PrEP), HIV risk was reduced by 50%, even when participants reported no condom use with regular (non-paying) partners and 70% use with clients. This is despite a 60% increase in these participants’ likelihood of STI exposure.

The study provides important insight for South Africa, which began rolling out PrEP for sex workers in June 2016. Most importantly, it identifies certain factors that programmers should track in order to identify female sex workers’ HIV risk.

For example, among female sex workers who report high levels of condom use with clients initially, yet are likely to move away from using condoms after initiating PrEP and are anticipated to adhere poorly to PrEP, HIV risk is likely to rise.

By contrast PrEP could be an important addition to combined HIV prevention for female sex workers who are less likely to use condoms with clients in the first instance, or who are anticipated to adhere reasonably well to PrEP.

The authors conclude that their study “demonstrates that the success of PrEP will rest upon its ability to achieve high enough PrEP adherence in female sex workers such that the increased protection achieved outweighs the increased HIV risk… The added value for decision makers of our study lies upon our ability to quantify these trade-offs.”

Despite the insight the study provides, it also has a number of limitations. Crucially, it does not address the fact that inadequate adherence to PrEP could increase someone’s risk of developing antiretroviral (ARV) resistance. Neither does it examine the stage of HIV infection or ARV use among partners, both of which are significant factors to consider when examining HIV risk.

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Written by Caitlin Mahon

Content Specialist - HIV & Sexual Health