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Impact of five years of peer-mediated interventions on sexual behavior and sexually transmitted infections among female sex workers in Mombasa, Kenya
Global Health Sciences Literature Digest
Published August 07, 2008
Journal Article

Luchters S, Chersich MF, Rinyiru A, Barasa MS, King'ola N, Mandaliya K, et al. Impact of five years of peer-mediated interventions on sexual behavior and sexually transmitted infections among female sex workers in Mombasa, Kenya. BMC Pub Health 2008 April 29;8(1):143. Epub.


To evaluate the effect of five years of peer-mediated STI/HIV prevention interventions among female sex workers (FSWs) in Mombasa, Kenya

Study Design

A five-year peer intervention evaluated with two cross-sectional surveys of FSWs (pre- and post-) using snowball sampling


The study took place in Mombasa, Kenya, a port city and major economic center with a large FSW population, in the Kisauni division, which has around 250,000 inhabitants and 70,000 households.


FSWs, defined as any woman who reported having received money or gifts in exchange for sex in the past year. FSWs work either full- or part-time from bars, hotels, streets, and homes. They also frequently are involved in other small businesses, including selling foodstuffs and, in some areas, local brew, on the roadside.


In 2000, 62 FSWs from the Kisauni division were selected and trained as peer educators, 57 of whom were retained throughout the five-year period. Peer educators were selected through key informants, such as bar maids and patrons, at identified hotspots in the area. Study staff aimed to select FSWs who were willing to be peer leaders, had a substantial network of peers, were likely to remain in the area for an extended period, and had some knowledge of the key topics. The FSWs attended a five-day training course on STI/HIV signs and symptoms; STI/HIV prevention and treatment; promotion and distribution of male and female condoms; and teaching safe-sex negotiation skills. Six-day advanced and three-day refresher training was provided midway through the project. Peer educators acted as links between the local FSW community and the project, facilitating local involvement and participation. They conducted one-on-one or weekly group intervention sessions, mostly in FSWs' homes or at a drop-in center within the community. Besides functioning as a training and meeting facility, the drop-in center was used for distributing information, education, and communication (IEC) materials and condoms, and for providing voluntary counseling and testing (VCT) services. To transfer knowledge and health promotion messaging, diverse media were used, such as peer-mediated drama, role-playing exercises, picture codes (i.e., visual images used for engaging discussion on sensitive topics), and video. Peer-led activities occurred throughout the five-year period at a relatively constant rate. Peer educators also led monthly community gatherings with active participation of FSWs, youth, and other community members. These people provided HIV education, condom promotion, and other risk reduction activities and were accompanied by mobile VCT services, facilitating entry to HIV testing. A field coordinator updated peer educators on new developments in HIV prevention and regularly attended peer-education sessions to monitor the accuracy of information given and to respond to questions.

The pre- and post-intervention cross-sectional surveys occurred over a two-month period, in February-March 2000 and October-November 2005. To enhance comparison, the repeat survey adhered to the design and methodology of the pre-intervention survey. In brief, initial respondents (seeds) were identified from bars, guest houses, and the street, with subsequent participants recruited using snowball sampling. To limit the potential for friendship bias, the maximum number of women recruited through one participant was restricted to 10. Eligible participants were self-reported FSWs older than 16 years working within Kisauni. Peer educators were excluded from participation in the repeat survey. Study procedures were performed by qualified staff at the drop-in center. These procedures included structured questionnaires; VCT; collection of blood plasma and urine samples; and gynecological examination, with speculum insertion and collection of endocervical and high vaginal swabs. Where indicated, FSWs received STI treatment, as per the Kenya STI guidelines, free of charge. Women were encouraged to learn their HIV status and were offered same-day HIV testing and counseling, using onsite serial testing. Those who tested positive for HIV infection were referred to a comprehensive HIV care clinic where antiretroviral treatment is provided at no cost.

Primary Outcomes

Changes in HIV-related knowledge, attitudes, and behavior and in STI and HIV prevalence


In 2000, 503 FSWs were surveyed and in 2005, 506 FSWs. Although the proportion of single women remained unchanged, in 2000 a substantial proportion (39.4%) of the women were married or cohabiting, compared with only 2.5% in 2005. Only small changes were seen in age and income. Sex work had changed from a predominately part-time to a full-time activity; women with an alternative source of income decreased from 67.0% to 37.7% (P<0.001). The mean number of sexual partners increased from 2.8 to 4.9 per week (P<0.001). Merely 7.0% of women had four or more one-time clients per week in 2000; this percentage increased to 33.2% in 2005 (OR=6.6, 95% CI=4.4-10.2; P<0.001). Awareness of HIV status increased from 5.2% to 40.2% of the women.

In the 2005 survey, 28.7% (145/506) of women reported having attended peer-mediated interventions at least once. In the past six months, 78.6% (114/145) of these women had attended peer-education sessions a median of four times (IQR 2-7). Eighty-four percent (122/145) of FSWs who attended peer education had one-on-one sessions with peer educators. Individuals exposed to peer education had more consistent condom use with clients (86.2% vs. 64.0%; P<0.001). After adjusting for age, marital status, place of work, and education, peers were 2.3 times more likely to suggest condom use (95% CI=1.0-5.5; P=0.05) and 1.7 times more likely to refuse clients unwilling to use condoms (95% CI=1.0-2.8; P=0.04). No change was seen in use with emotional partners: 80% of women did not use condoms consistently. When comparing amount of STIs in FSWs receiving with those not receiving peer interventions, no significant differences were noted, but all differences were in the same direction. When comparing HIV prevalence in 2000 and 2005, a non-significant increase was noted: 30.6% (151/493) of women were infected in 2000 versus 33.3% (166/498; P=0.36) in 2005. No difference was seen among younger women aged 15-19 years (15%, 4/27 vs. 15%, 4/26; P=0.95).


Study findings suggest that peer-mediated interventions can change sexual behavior in FSWs, but do not lower the prevalence of HIV among FSWs, even among those in younger age groups. In addition, results suggest that additional strategies are needed to improve the coverage and effect of peer interventions.

Quality Rating

There is no quality assessment tool for pre-post intervention studies such as this. Some potential limitations were: 1) the study design and the absence of controls limit the ability to quantify effectiveness, especially because marked changes occurred in the study population, possibly resulting from an expansion in tourism and number of bars, with concomitant FSW in-migration; 2) the snowball sampling method may have produced non-comparable samples; and 3) many outcomes were self-reported and thus subject to social-desirability bias.

In Context

These findings are encouraging and consistent with previous studies which evaluated the ability of peer-mediated interventions to facilitate behavior change among high-risk groups,(1,2,3,4) although they are not consistent with all studies.(5) The absence of an effect on HIV prevalence is discouraging, although biases due to study design or temporal trends, such as improved HIV treatment, may explain the lack of decline in prevalence. The large increase in the proportion of sampled women engaged in full-time versus part-time sex work in 2005 may reflect larger economic changes in Mombasa or may be due to bias introduced by the study design/sampling method.

Programmatic Implications

Peer-based interventions are a relatively cost-effective way to attempt risk reduction and are particularly appropriate for hard-to-reach or stigmatized populations such as FSWs. This study, like most previous studies of peer interventions, shows some evidence of effectiveness in reaching FSWs and reducing risk in an urban setting. It also shows, with the high retention rate (57/62) of peer FSWs over five years, that such interventions can be sustained long term.


  1. Tawil O, O'Reilly K, Coulibaly IM, Tiemele A, Himmich H, Boushaba A, et al. HIV prevention among vulnerable populations: outreach in the developing world. AIDS 1999;13 Suppl A:S239-47.
  2. Rekart ML. Sex-work harm reduction. Lancet 2005;366(9503):2123-34.
  3. Boily MC, Lowndes C, Alary Amirkhanian YA, Kelly JA, Kabakchieva E, Kirsanova AV, et al. A randomized social network HIV prevention trial with young men who have sex with men in Russia and Bulgaria. AIDS 2005;19(16):1897-1905.
  4. Gregson S, Adamson S, Papaya S, Mundondo J, Nyamukapa CA, Mason PR, et al: Impact and process evaluation of integrated community and clinic-based HIV-1 control: A cluster-randomised trial in eastern Zimbabwe. PLoS Med 2007;4(3):e102.
  5. 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; 82 Suppl 1:i21-6.