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Sustained changes in sexual behavior by female sex workers after completion of a randomized HIV prevention trial
Global Health Sciences Literature Digest
Published November 5, 2007
Journal Article

Ngugi EN, Chakkalackal M, Sharma A, Bukusi E, Njoroge B, Kimani J, et al. Sustained changes in sexual behavior by female sex workers after completion of a randomized HIV prevention trial. J Acquir Immune Defic Syndr 2007 Aug 15;45(5):588-94.


To examine the sustainability of behavioral interventions on sexual behavior of female sex workers (FSWs) after the completion of a sexually transmitted infection (STI) and HIV-prevention clinical trial.

Study Design

Observational cohort study carried out one year after the completion of a randomized placebo-controlled double-blind STI and HIV-prevention study.


Kibera district in Nairobi, Kenya, which is a slum comprising 10 villages.


High-risk Kenyan FSWs who had completed the baseline enrollment questionnaire for the randomized trial, had been followed for varying intervals of time through the trial, and had completed the re-survey questionnaire. An FSW was defined as a woman who reported receiving money or gifts in exchange for sex during the month before initial screening.


From 1998 to 2002, HIV-seronegative FSWs were enrolled in a randomized placebo-controlled clinical trial where a prophylaxis antibiotic, azithromycin, was administered monthly to prevent STIs and HIV in study participants. Participants were provided with clinic-based HIV prevention services that included free male condoms, treatment of symptomatic STIs, twice-yearly screening and treatment of asymptomatic STIs, and sexual risk reduction counseling. Clinic-based counseling was provided at enrollment and each monthly visit, and HIV counseling and testing were performed every three months. Participants also attended quarterly peer-led and researcher-supported community meetings held in each village. Discussion in these meetings focused on risk reduction. All clinic-based counseling and testing services ended after trial completion, except for the quarterly peer-led community meetings. A local project also started distributing free female and male condoms throughout sex work hotspots. A little over a year after trial termination, participants still residing in Kibera were invited to participate in a cohort re-survey by completing a behavioral questionnaire and undergoing HIV/STI counseling and testing. HIV screening was performed by enzyme-linked immunosorbant assay and confirmed with the Recombigen enzyme assay. Urine samples were analyzed by polymerase chain reaction for Neisseria gonorrhoeae and Chlamydia trachomatis. Trichomonas vaginalis was cultured from vaginal swabs. Syphilis serology was also performed. Treatment was provided as needed according to Kenyan national guidelines.

Primary Outcomes

Primary outcomes were mean charge for sex, number of casual clients per week, mean number of regular clients, self-reported condom use with casual and regular clients, STIs and HIV incidence. Data from the re-survey were compared with those collected at baseline and at completion of the randomized trial.


One hundred seventy-two out of the 466 FSWs (36.9%) from the randomized trial were re-surveyed, of whom 144 (84%) currently exchanged sex for money. The mean age at re-survey was 33.5 years (+/- 8.8 years), and the mean time since last clinical trial visit to re-survey was 1.2 years (range: 1.0 to 5.3 years). The mean reported duration of sex work was 10.5 years (+/- 6.7 years). Characteristics of those taking part in the re-survey were compared to those who did not. FSWs who were re-surveyed were older at trial enrollment (30.0 vs. 27.8 years, p=0.002), but there were no significant differences between the two cohorts in charge for sex, baseline sexual behavior (defined by condom use with casual or regular clients, anal sex, or sex during menses), or prevalence of infection by N. gonorrhoeae, C. trachomatis, or T. vaginalis. At re-survey, the mean charge for sex had increased significantly from trial enrollment (201 vs. 131 Kenyan shillings; p<0.001). The reported number of casual clients per week had increased significantly since the last study visit (2.8 at last study visit vs. 6.1 at re-survey, p<0.001), although casual client numbers remained much lower at re-survey than they had been at the original trial enrollment (6.1 v 16.2, p<0.001). Condom use with casual clients had continued to increase from the completion of the original trial (2.6/5 at enrollment; 3.7/5 at last study visit vs. 4.3/5 at re-survey, p<0.001). Based on these self-reported numbers, the number of annual unprotected sexual encounters with casual clients for each FSW was calculated to be 23.6 per year at the end of the original trial, a 15-fold decrease from 393.2 per year at trial enrollment (p<0.001). This number increased by the time of re-survey (from 23.3 to 35.6 per year, p=0.05). Among the 144 women who had remained active in sex work, 68 (47%) had reported a regular client at enrollment, and 107 (74%) did so at re-survey. The mean number of regular clients had increased from 0.9 at enrollment (range: 1 to 5 clients) to 1.3 at re-survey (range: 1 to 5 clients) (p<0.001). Self-reported condom use had increased substantially, from 1.1/5 to 3.5/5 (p<0.001) over this period. Condom use with regular clients, however, was consistently lower than with casual clients at enrollment (1.1/5 with regular clients vs. 3.2/5 with casual clients, p<0.001) and at re-survey (3.5/5 with regular clients vs. 4.3/5 with casual clients, p<0.001). The proportion of all unprotected sexual encounters that were with a regular client, as opposed to a casual client, increased from 10.3% at enrollment to 34.6% at re-survey; (p<0.001). At re-survey, the greatest increase in client numbers was seen in bar-based sex workers (5.2 clients since trial termination), compared to home-based (2.2 clients) and club-based (3.8 clients) sex workers (p=0.001). Self-reported condom use did not differ amongst the different groups. HIV incidence was 3.7 per 100 person-years (PYs) during the trial, compared to 1.6/100 PYs at re-survey (p=0.3). STI prevalence at re-survey was also found to be lower than at enrollment (2.4% vs. 7.5% for chlamydia, p=0.03; 4.2% vs. 8.1% for gonorrhea, p=0.1; and 0% vs. 14.2% for trichomoniasis, p<0.001). FSWs with a prevalent STI or newly acquired HIV infection (compared to those without) reported a higher number of unprotected sexual encounters with casual clients over the past year (83.2 vs. 37.4, p=0.009). These FSWs were also younger (27.3 vs. 33.5 years of age, p=0.009) and had been engaged in sex work for a shorter time (6.6 vs. 10.4 years, p=0.02). The number of unprotected sexual encounters with regular clients per year was not associated with new STI/HIV infection (25.7 vs. 24.8, p=0.9).


The authors conclude that, although the risk reduction intervention provided in this study falls short of the more resource-intensive best practices suggested by UNAIDS,(1) changes in sexual behavior and reduced STI and HIV rates among FSWs can be sustained if a low level of community-based risk reduction services can be maintained. The authors also noted that further follow-up is required to see how long these changes can be sustained.

Quality Rating

According to the Newcastle-Ottawa quality rating of observational cohort studies, this study receives a fair rating. Limitations to the study include: 1. The study only examined changes in sexual behavior on an individual level; 2. the study could not demonstrate whether the observed behavioral changes represented a natural evolution of sex work practices as women age, or if they are a reflection of changes induced by the provided community-based peer intervention; 3. the study could not demonstrate whether the observed behavioral changes were limited to individuals enrolled or if they were occurring at a larger community level;(2) 4. self-reported data may be unreliable.

In Context

Several programs, such as the Sonagachi model of a sustainable community-level HIV intervention(3) and the Thailand 100% condom use program,(4,5) have led to sustained changes in sexual behavior among FSWs.(6,7,8) However, studies in Cameroon demonstrated poor sustainability of changes in sexual behavior after a short-term intervention.(9)

Programmatic Implications

FSWs are one of the highest-risk HIV populations in regions of the world most affected by the HIV pandemic.(10,11) Interventions among FSWs are among the most cost-effective public health strategies available to curb HIV transmission.(12,13)

Hence, sustainable low-cost community-level interventions that can lead to sustained changes in sexual behavior are important in reducing STI and HIV rates. Although the number of clients increased at the time of re-survey, the increase in condom use is encouraging. The increase in regular clients compared to casual clients and the lower rates of condom use with regular clients, however, are a concern. Although this study did not find an association between unprotected sex with regular clients and STIs/HIV rates, regular clients are believed to represent an important bridging population for STIs/HIV between sex workers and the general population. Additionally, the results of this study should be interpreted with caution, given that it only looked at the individual level in one region and outcomes may reflect trends unrelated to the intervention. More intensive behavioral interventions may still be needed to have an impact, particularly on younger sex workers who are at greater risk for STI/HIV acquisition.


  1. United Nations Program on HIV/AIDS. JUNPoHA. UNAIDS technical update: sex work and HIV/AIDS. UNAIDS Best Practice Collection. Geneva, Switzerland United Nations Programme on HIV/AIDS (UNAIDS); 2002. (No abstract available.)
  2. Cheluget B, Baltazar G, Orege P, Ibrahim M, Marum LH, Stover J. Evidence for population level declines in adult HIV prevalence in Kenya. Sex Transm Infect 2006 Apr;82 Suppl 1:i21-6.
  3. Basu I, Jana S, Rotheram-Borus MJ, Swendeman D, Lee SJ, Newman P, et al. HIV prevention among sex workers in India. J Acquir Immune Defic Syndr. 2004 Jul 1;36(3):845-52.
  4. Rojanapithayakorn W, Hanenberg R. The 100% condom program in Thailand. AIDS 1996 Jan;10(1):1-7. Review. (No abstract available).
  5. Rojanapithayakorn W. The 100% condom use programme in Asia. Reprod Health Matters 2006 Nov;14(28):41-52.
  6. Ngugi EN, Wilson D, Sebstad J, Plummer FA, Moses S. Focused peer-mediated educational programs among female sex workers to reduce sexually transmitted disease and human immunodeficiency virus transmission in Kenya and Zimbabwe. J Infect Dis 1996 Oct;174 Suppl 2:S240-7.
  7. Ghys PD, Diallo MO, Ettiegne-Traore V, Kale K, Tawil O, Carael M, et al. Increase in condom use and decline in HIV and sexually transmitted diseases among female sex workers in Abidjan, Cote d'Ivoire, 1991-1998. AIDS 2002 Jan 25;16(2):251-8.
  8. Ghys PD, Diallo MO, Ettiegne-Traore V, Satten GA, Anoma CK, Maurice C, et al. Effect of interventions to control sexually transmitted disease on the incidence of HIV infection in female sex workers. AIDS 2001 Jul 27;15(11):1421-31.
  9. Wong EL, Roddy RE, Tucker H, Tamoufe U, Ryan K, Ngampoua F. Use of male condoms during and after randomized, controlled trial participation in Cameroon. Sex Transm Dis 2005 May;32(5):300-7.
  10. Plummer FA, Nagelkerke NJ, Moses S, Ndinya-Achola JO, Bwayo J, Ngugi E. The importance of core groups in the epidemiology and control of HIV-1 infection. AIDS 1991;5 Suppl 1:S169-76. Review.
  11. Jha P, Nagelkerke JD, Ngugi EN, Prasada Rao JV, Willbond B, Moses S, et al. Public health. Reducing HIV transmission in developing countries. Science. 2001 Apr 13;292(5515):224-5. (No abstract available).
  12. Alary M. More community-based trials of STD control or more appropriate interventions: which is the priority for preventing HIV-1 infection in developing countries? Bull World Health Organ 2001;79(1):59-60. (No abstract available).
  13. Doherty IA, Shiboski S, Ellen JM, Adimora AA, Padian NS. Sexual bridging socially and over time: a simulation model exploring the relative effects of mixing and concurrency on viral sexually transmitted infection transmission. Sex Transm Dis 2006 Jun;33(6):368-73.