Need for scaled up combination prevention for sex workers, Indian and Central American studies show

Presentations given at a session considering HIV prevention strategies among female sex workers, which took place at the 20th International AIDS Conference (AIDS 2014) in Melbourne, Australia, show that while consistent condom use is generally high among female sex workers, other barriers remain to effective prevention of HIV transmission and to care for those who are living with HIV.

Importantly, while condom use by female sex workers with their clients is notably high in some populations, the same populations report lower rates of condom use with regular partners, pointing to a potential blind spot in HIV prevention strategies, potential for transmission, and potential behavioural, psychological, social and other barriers to partner condom use. The session, titled "Successful HIV Prevention Strategies with Female Sex Workers," included a discussion of different models which aim to help to prevent infections among female sex workers and other vulnerable populations, ranging from combination prevention efforts that rely on behavioural, biomedical, and structural interventions, to the use of oral pre-exposure prophylaxis (PrEP).

Central America: Combination prevention for female sex workers

Jorge Rivas of the Pan American Social Marketing Organization (PASMO), presented a study that considered the impact of combination prevention on condom use with both clients and regular partners, and HIV testing, among female sex workers in six Central American countries, Guatemala, El Salvador, Nicaragua, Costa Rica, Panama, and Belize. The study, part of a combination prevention programme taking place from 2010-2015, included 3293 female sex workers, aged 18 to 49.

PASMO found that condom use with clients was already often very high, with over 80% of sex workers in most countries reporting consistent condom use with clients (Belize was the outlier, where only 60% of female sex workers reported consistent condom use with clients). Condom use with regular partners, however, was significantly lower: only 30% of female sex workers in El Salvador and Guatemala, for example, reported consistent condom use with regular partners. Panama and Costa Rica had the highest percentages, but still only approximately 60% of female sex workers reported regular condom use with partners there. Reported HIV testing within the last 12 months varied widely between countries, with only 65% of sex workers in Belize having had an HIV test, compared to nearly 100% in Costa Rica.

Perhaps, Rivas suggested, because condom use with clients is already very high in all six countries, none of the interventions – behavioral (such as behaviour change communication activities), biomedical (such as voluntary HIV counseling and testing), or structural (such as referral to drug and alcohol treatment programmes) – either individually or in tandem, affected condom use with clients. However, with regards to condom use with regular partners, behaviour interventions had a positive impact in Costa Rica and Belize (with female sex workers 2.73 times and 3.8 times more likely to use condoms, respectively), behavioural and biomedical interventions together had a positive impact in Costa Rica and Panama (3.54 and 2.35 times more likely, respectively), and biomedical, biological, and structural interventions together having a positive impact in El Salvador (with female sex workers 2.3 times more likely to use condoms with regular partners). HIV testing was unaffected by any of the interventions.

Pointing to the study's findings that behavioural and biomedical interventions together had a more significant impact on use of condoms with regular partners, as compared to just behavioural interventions, in Costa Rica, Rivas concluded that "combination prevention strategies can have a positive impact on condom use with regular partners." Rivas offers that the study relies on after-the-fact self-reporting from female sex workers, so may be prone to recall bias and to over- or under-reporting.

Interestingly, Belize – which fared significantly worse in condom use with clients and HIV testing in the last 12 months, but better than some other countries when considering condom use with regular partners – is the only country of the six where sex work is illegal, according to Rivas.

India: Modelling the impact of pre-exposure prophylaxis in sex workers and men who have sex with men

Both female sex workers and men who have sex with men (MSM) in Bangalore, India, also report high rates of condom use with high-risk partners, ranging from 75 to 90%, but much lower rates of condom use with long-term, heterosexual partners, according to a presentation given by Kate Margaret Mitchell of the London School of Hygiene and Tropical Medicine.

Mitchell presented a mathematical modelling study that considers the potential preventive impacts of oral PrEP – taken by female sex workers and/or MSM in Bangalore – on these high-risk populations, and on the population as a whole. While the impact of oral PrEP has been studied in MSM and heterosexual couples, the impact on female sex workers has not yet been studied, although several projects are planned or currently underway. Mitchell’s study was done in preparation for two planned demonstration programmes in Kolkata and Mysore. As of 2009, 8% of Bangalore’s female sex workers and 16.5% of the city's MSM were living with HIV.

The model considered behavioural data (such as number of partners and frequency of condom use) from surveys, and biological data (such as likelihood of HIV transmission per sex act) from literature, and considered an estimated 12,000 female sex workers and 18,000 MSM who were already in contact with HIV or other services, and therefore likely to be able to access PrEP. Estimating a 40% coverage rate and 60% efficacy (which considers both effectiveness of oral PrEP and adherence), Mitchell and her co-authors found that 23% of HIV infections in female sex workers could be averted within a decade if oral PrEP was offered to this population, with an overall 3.4% reduction in HIV infections in the general population. The impact from offering the intervention to MSMs was markedly lower, but offering oral PrEP to both female sex workers and MSM could result in a population-wide 6% decrease in HIV infections within 10 years.

Mitchell emphasised that the population-specific and population-wide impact significantly increases over time, with many more lives saved for far less resources over 20 years as compared to 10. As such, she suggests that policy makers and programme planners consider longer-term outcomes when looking at both cost and efficacy of providing PrEP to these high-risk populations.

Zimbabwe: Need for expanded access to HIV testing and ART for sex workers

Frances M Cowan of the SAPPH-IRe programme in Zimbabwe also offered high estimates of condom use among female sex workers and their clients, with 60% of sex workers reporting regular condom use. Cowan's presentation offers results from a baseline survey conducted at the start of an 18-month study that will consider the impact and cost of additional interventions, such as PrEP and on-site antiretroviral therapy (ART), on HIV prevention among female sex workers, as compared to the package of services currently offered by SAPPHI-IRe, such as health education and HIV counselling and testing. (SAPPH-IRe stands for Sisters Antiretroviral therapy Program for Prevention of HIV-an Integrated Response, a collaborative project between the Zimbabwe Ministry of Health and international partners.)

From 13 November to 20 December 2013, 2722 female sex workers took part in the survey. The mean age was 32 years (range 18 to 65), and the majority had started sex work sometime between age 20 and 24 (although 18% started before the age of 18). Self-reported instances of intimate partner violence were high, at 34.7%, 28.3% from clients. 4.3% of female sex workers had been raped in the last 12 months.

Despite high rates of self-reported condom use with clients, HIV prevalence among the population was very high, at 56.4%. Only 61% of those who were living with HIV reported knowing their status. Forty per cent of female sex workers living with HIV said they were taking ART, with 31% of these having an undetectable viral load. (Cowan notes potential reporting bias, given that 14% of female sex workers who were living with HIV had an undetectable viral load, despite saying they were not on ART.)

The outcomes of the study show that while access to services for female sex workers is increasing in Zimbabwe (2011 research noted that only 25 to 35% of female sex workers were on ART, as compared to SAPPH-Ire’s 40%), it is still inadequate, particularly with regards to testing and diagnosis.