PLoS ONE plos plosone PLOS ONE 1932-6203 Public Library of Science San Francisco, CA USA 10.1371/journal.pone.0288717 PONE-D-22-24072 Research Article Social sciencesSociologySexual and gender issuesSex work Medicine and health sciencesEpidemiologyMedical risk factorsTraumatic injury risk factorsViolent crime Medicine and health sciencesPublic and occupational healthTraumatic injury risk factorsViolent crime Social sciencesSociologyCriminologyCrimeViolent crime Medicine and health sciencesPublic and occupational healthPreventive medicineHIV prevention Social sciencesLaw and legal sciencesCriminal justice systemLaw enforcementPolice People and placesPopulation groupingsProfessionsPolice Biology and life sciencesMicrobiologyMedical microbiologyMicrobial pathogensViral pathogensImmunodeficiency virusesHIV Medicine and health sciencesPathology and laboratory medicinePathogensMicrobial pathogensViral pathogensImmunodeficiency virusesHIV Biology and life sciencesOrganismsVirusesViral pathogensImmunodeficiency virusesHIV Biology and life sciencesOrganismsVirusesImmunodeficiency virusesHIV Biology and life sciencesOrganismsVirusesRNA virusesRetrovirusesLentivirusHIV Biology and life sciencesMicrobiologyMedical microbiologyMicrobial pathogensViral pathogensRetrovirusesLentivirusHIV Medicine and health sciencesPathology and laboratory medicinePathogensMicrobial pathogensViral pathogensRetrovirusesLentivirusHIV Biology and life sciencesOrganismsVirusesViral pathogensRetrovirusesLentivirusHIV People and placesPopulation groupingsProfessionsSex workersFemale sex workers Medicine and health sciencesEpidemiologyMedical risk factors Computer and information sciencesComputer networksInternet Changes in context, typology and programme outcomes between early and recent periods of sex work among young female sex workers in Mombasa, Kenya: A cross-sectional study Changes in context, typology and programme outcomes among young female sex workers in Mombasa, Kenya https://orcid.org/0000-0003-3277-7693 Bhattacharjee Parinita Conceptualization Formal analysis Writing – original draft Writing – review & editing 1 2 * Isac Shajy Conceptualization Data curation Formal analysis Methodology Writing – review & editing 1 Musyoki Helgar Supervision Writing – review & editing 3 Gichangi Peter Project administration Supervision Writing – review & editing 4 Ma Huiting Formal analysis Visualization Writing – review & editing 5 https://orcid.org/0000-0002-9235-0547 Becker Marissa Conceptualization Funding acquisition Methodology Project administration Supervision Writing – review & editing 1 Hontelez Jan Supervision Validation Writing – review & editing 6 7 https://orcid.org/0000-0001-8492-5470 Mishra Sharmistha Conceptualization Funding acquisition Methodology Resources Supervision Writing – review & editing 5 8 9 on behalf of the Transitions team Institute for Global Public Health, University of Manitoba, Winnipeg, Canada Partners for Health and Development in Africa, Nairobi, Kenya National AIDS and STI Control Programme, Ministry of Health, Nairobi, Kenya International Centre for Reproductive Health- Kenya, Mombasa, Kenya St. Michael’s Hospital, Unity Health Toronto, Toronto, Canada Department of Public Health, Erasmus MC, Rotterdam, Netherlands Heidelberg Institute of Global Health, Heidelberg University, Heidelberg, Germany Institute of Medical Sciences, University of Toronto, Toronto, Canada Institute of Health Policy Management and Evaluation, Dalla Lana School of Public Health, University of Toronto, Toronto, Canada Blumenthal Jill Editor University of California San Diego, UNITED STATES

The authors have declared that no competing interests exist.

¶ Complete membership of the author group can be found in the Acknowledgments.

 * E-mail: Bhattacharjee.parinita@gmail.com 25 7 2023 2023 18 7 e0288717 4 9 2022 4 7 2023 2023 Bhattacharjee et al This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Introduction

The sex work context and typology change continuously and influence HIV related risk and vulnerability for young female sex workers (YFSW). We sought to describe changes in the context and typology of sex work between the first (early) and past month (recent) of sex work among YFSW to inform HIV prevention programming for sex workers.

 Methods

We used data from a cross-sectional survey (April-November 2015), administered using physical location-based sampling to 408 cis-women, aged 14–24 years, who self-identified as sex workers, in Mombasa, Kenya. We collected self-reported data on the early and recent month of sex work. The analysis focused on changes in a) sex work context and typology (defined by setting where sex workers practice sex work) where YFSW operated, b) primary typology of sex work, and c) HIV programme outcomes among YFSW who changed primary typology, within the early and recent month of sex work. We analysed the data using a) SPSS27.0 and excel; b) bivariate analysis and χ2 test; and c) bivariate logistic regression models.

 Results

Overall, the median age of respondents was 20 years and median duration in sex work was 2 years. Higher proportion of respondents in the recent period managed their clients on their own (98.0% vs. 91.2%), had sex with >5 clients per week (39.3% vs.16.5%); were able to meet > 50% of living expenses through sex work income (46.8% vs. 18.8%); and experienced police violence in the past month (16.4% vs. 6.5%). YFSW reported multiple sex work typology in early and recent periods. Overall, 37.2% reported changing their primary typology. A higher proportion among those who used street/ bus stop typology, experienced police violence, or initiated sex work after 19 years of age in the early period reported a change. There was no difference in HIV programme outcomes among YFSW who changed typology vs. those who did not.

 Conclusions

The sex work context changes even in a short duration of two years. Hence, understanding these changes in the early period of sex work can allow for development of tailored strategies that are responsive to the specific needs and vulnerabilities of YFSW.

 Canadian Institutes of Health Research (CIHR) MOP 13044 CIHR FDN 13455 BMGF INV006613 https://orcid.org/0000-0003-3277-7693 Bhattacharjee Parinita The study was funded by an operating grant (MOP-13044) from the Canadian Institutes of Health Research (CIHR) and analyses funded via CIHR grant FDN 13455. MB, SM were supported by CIHR grants - MOP 13044 and FDN13455. PB was supported by BMGF grant - INV006613. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. There was no additional external funding received for this study. Data Availability The data contain information related to locations where young women who sell sex conduct sex work. Sex work and sex workers are criminalised in Kenya, hence the data is sensitive. Data are available on request from the IGPH - University of Manitoba Data Manager, Stella Leung, Stella.Leung@umanitoba.ca. Introduction

Limited information on the context and settings of sex work during the early period of sex work poses a significant challenge for HIV prevention programmes to design and adapt services to reach women at the time they enter sex work [1]. There are several studies that show that the setting in which women practice sex work, and context in which sex work takes place, changes over time [2–4] but very few studies have attempted to understand these changes [5]. The importance of understanding the context and organization of the sex work industry [6–8] and different settings [9] particularly during the early stages of sex work [10] is gaining increasing attention from HIV prevention programmes to ensure that delays in HIV programme contact for young female sex workers (YFSW) 15–25 years, are reduced and interventions strategies are developed to effectively address their specific needs and vulnerabilities.

The ways in which sex work is practiced are diverse and change over time responsive to sociocultural, economic or technological context [11, 12]. Both context and setting of sex work affect the health and personal safety of sex workers, as identified by Harcott et al [13]. One of the critical changes in the setting in which sex workers work can be understood and described as the typology of sex work. Typology of sex work is defined as the classification of female sex workers (FSW) into types, or categories, based on the settings in which they practice sex work such as street setting or lodge setting [14]. Understanding typology is important as sex workers in different settings experience a range of unique risks and vulnerabilities and therefore require targeted programming strategies [15–18]. Several studies across countries have found that HIV and other sexually transmitted infections (STI) prevalence among FSWs [19, 20] and the reach of the HIV prevention programmes [21], differ by sex work typologies. Differences in the context and working conditions in varied sex work typology can influence sex work practices and potential risks of HIV infection [22]. There can be different clusters of risk factors associated with different typology of sex work, thus demanding prevention programmes to tailor interventions based on typology of sex work [23]. Sex work typologies are not static as FSWs constantly change their settings. Mishra et al. in their study in Nepal found that the changing typology of sex work increases the vulnerability of sex workers to STI and HIV infections as these changes result in the sex workers getting cutoff from HIV programmes due to low awareness of programmes in the new locations, posing challenges for them to access information and services [24]. Understanding the diversity in sex work typology and the context of sex work is crucial for assessing the risk of acquiring and transmitting HIV and other STIs among FSW [25, 26]. It also has important implications for planning and implementing effective HIV and STI interventions that are tailored to the specific needs of this population [8, 9, 16, 27–29].

YFSW are at particularly heightened risk of HIV in Africa [30]. In addition to the physiological, emotional and social vulnerabilities faced by adolescent girls and young women as they transition into adulthood, YFSW face added challenges related to stigma, discrimination and criminalisation [31, 32], and reduced ability to negotiate condom use with sexual partners [4]. Most HIV prevention programmes tailored for FSWs are designed to reach women several years after entering sex work or self-identifying as sex worker [33]. It is important to understand the changes in the context and typology of sex work during the early period of sex work in order to design effective time–period tailored HIV prevention interventions for YFSW who are just beginning sex work.

In this paper we sought to describe the changes in context and typology of sex work and programme outcomes during the first (early) and past (recent) month of sex work among YFSW in Mombasa, Kenya. We describe the changes in a) context of sex work; b) distribution of typologies of sex work including extent and patterns of overlap; and c) primary typology of sex work within person, during the early and recent periods of sex work. Then we describe the characteristics of YFSW during the early period of sex work for those sex workers who change their primary typology. In addition, we compare and describe the programme outcomes specifically prevalent HIV infection, HIV programme reach and service utilization among those YFSW who change their primary typology during the early and recent period of sex work vs. those who do not.

 Methods

We used data from a bio-behavioural cross-sectional survey, administered between April and November 2015, to sexually active cis gender adolescent girls and young women aged 14–24 years frequenting sex work physical locations in Mombasa, Kenya. Sex work locations included any locale or setting where individuals solicited clients for sex or provided sex services in exchange for money [34]. Eligibility criteria for the survey included: sexually active females, aged 14–24 years, and provision of written informed consent. Consent was obtained from participants directly to participate in the study. Written informed consent from the participants’ legal guardian/next of kin was not required for participation in this study in accordance with the national legislation and the institutional requirements [35]. For the paper, we restricted our analyses to data on 408 participants who self-identified as sex workers.

We identified sex work locations using geographic mapping [36], which also provided the distribution and population size of YFSW. The list of sex work locations, served as the sampling frame, and a sample of 85 locations were selected via probability proportional to the estimated YFSW population size at each location. Peer/community researchers (i.e. current or former sex workers engaged with International Centre for Reproductive Health–Kenya (ICRH-K)), a local HIV prevention organisation, went to the sampled locations and selected potential participants for eligibility screening and consent as detailed previously [37]. Trained interviewers used structured questionnaires to conduct face-to-face interviews in English or Kiswahili. Details of the data collection have been detailed previously [38].

The participants were reimbursed Ksh 850 for their time. The survey took 1 hour and 30 minutes including the collection of biological samples. The survey took place in private spaces that were located within the Drop-in Centres and clinics managed by ICRH-K or government clinics identified by the peer educators as safe and friendly spaces. All the rooms where the face-to-face interviews and biological sample collections took place had privacy for the respondents. All respondents were given a unique ID to protect confidentiality and this ID was attached to their questionnaire and biological sample. Hard copies of the filled questionnaires and other documents were stored in locked cabinets, accessible only by members of the research team. The electronic data was entered in a password protected computer and stored in a password protected server. Only the research team had access to the data.

Measurement and data analysis

In this paper, we define early period of sex work as the first month of sex work practice after the respondent self-identified herself as sex worker and recent period of sex work as the last month of sex work practice before the respondent participated in the survey. To understand the changes in sex work practices in the early and recent period of sex work, we used the following variables, a) management of sex work, b) number of paying clients per week, c) income from sex work to meet living expenses, d) experience of coercion in the past month and e) experience of police violence in the past month. Typology refers to the classification of YFSW based on settings in which sex work took place (either solicitation and/or site of the sexual service). We used the following question; how did you meet your paying clients in the first month of sex work and in the last month of sex work to define typology. The question was a multiple answer question with 15 response options. We combined the options to define five typologies of sex work, namely a) internet and mobile phone b) street and bus stop c) entertainment venue d) hotel and lodge and e) others. The others typology included places like home, school, church etc. We compared the typology distribution in the early to the recent period to identify any changes that may have occurred. Furthermore, we assessed the extent and pattern of overlap in the typology of sex work among the YFSWs during these two periods. To define primary typology in the paper, we used the question, of all the different places and ways you had met paying clients, which was the most common for the first month of sex work and the last month of sex work. We assessed within person change in primary typology between the early and recent period of sex work. Among YFSW who reported change in the primary typology of sex work, we examined their following characteristics during the early period of sex work: a) primary typology of sex work; b) management of sex work; c) meeting living expenses through income of sex work; d) number of paying clients per week; e) experience of physical violence in the past month; f) experience of coercion in the past month; g) experience of police violence in the past month; h) living condition and i) age at start of sex work. We then assessed the change in programme outcomes i.e. prevalent HIV infection, HIV programme reach and service utilisation among YFSW who changed their primary typology compared to those who did not. We used HIV test result (conducted on site) to assess the prevalent HIV infections. We used one questions to measure programme reach i.e. ever contacted by a peer or staff from Non-Governmental Organization (NGO)/ Community based Organisation (CBO)/ Faith based Organisation (FBO); and two questions to measure service utilisation namely a) ever tested for HIV and; b) ever used a clinic run by NGO/ CBO/ FBO.

Details of the questions used to define each variable is presented as S1 Table.

 Statistical analysis

The importance and value of descriptive work in epidemiology and public health is well established. Descriptive studies seek to characterize what is happening in the world to inform public health priorities and target interventions [39, 40]. We used descriptive statistics to describe the change in practice and context of sex work, change in typology distribution, extent and pattern of overlap in typology of sex work; and change in primary typology of sex work in early and recent period of sex work for YFSW. We also conducted sensitivity analysis to assess the change in primary typology of sex work by duration in sex work. We described the early period characteristics of those YFSW who changed their primary typology using bivariate analysis and χ2 test to assess the factors associated with the change in typology. We then assessed the programme outcomes (prevalent HIV infection, programme reach and service utilisation) for those FSW who changed their primary typology and compared with those who did not, using bivariate logistic regression models. We used SPSS27.0 and excel for statistical analyses and graphics and presented Odds Ratio (OR) and 95% Confidence Interval (CI).

 Inclusivity in global research

Additional information regarding the ethical, cultural, and scientific considerations specific to inclusivity in global research is included in S1 File.

 Ethics approval

The study received ethics approval from the Health Research Ethics Board at the University of Manitoba, Canada (HS16557 (H2013:295)) on 9th September 2014 and the Kenyatta National Hospital-University of Nairobi Ethics and Research Committee, Kenya (P497/10/2013) on 5th June 2014. The study also received a research permit from the National Commission for Science, Technology and Innovation (NACOSTI), Kenya.

 Results

Overall (Table 1), 42.2% of the YFSW respondents were less than 20 years with the median age being 20 years (IQR- 4), 69.6% had completed primary education, 16.5% had regular source of income, 58.1% respondents had their sexual debut between 15–19 years with the median age at sexual debut being 15 years (IQR– 3), 24.0% of the respondents were in sex work for less than one year and 40% were in sex work for 1–2 years, with the median duration being 2 years (IQR– 2).

10.1371/journal.pone.0288717.t001 Socio-demographic and sexual characteristics of young female sex workers who participated in the Transition study in Mombasa, Kenya, 2015.
Characteristics Percent N = 408
Age
    <20 years 42.2
    20–24 years 57.8
    Median age (years) 20.0 (IQR‡-4)
Education level  
    Upto Primary 30.4
    Primary complete 31.1
    Attended high school and above 38.5
Income
% currently have regular source of income§ 16.5
Age at first sex  
    <15 years 34.8
    15–19 years 58.1
    20–24 years 7.1
    Median age at sexual debut 15 years (IQR‡-3)
Duration in sex work  
    <1 years 24%
    1–2 years 40%
    3–4 years 23%
    5 years and more 13%
    Mean duration in sex work 2.2 years (SD† - 2.2)
Median duration in sex work 2 years (IQR‡ - 2)

†SD: Standard deviation

‡IQR: Interquartile range

§ The questionnaire did not clearly define the source of income so we cannot say whether source of income includes income from sex work or not

 Change in sex work practices, context and typology

Table 2 compares the sex work practices among YFSW in the early and recent period of sex work. Compared to the early period, at the recent period, a higher proportion of YFSW managed solicitation of clients independently without the use of a third party (pimp or manager) (91.2% vs 98.0%, p < 0.001), had more than 5 paying clients per week (16.5% vs 39.3%, p < 0.001), had higher mean number of paying clients per week (4.0 clients vs 5.7 clients, p <0.001), met more than half of their living expenses through the income of sex work (18.8% vs 46.8%, p < 0.001) and had experienced police violence in the past month (6.5% vs 16.4%, p <0.001). However, there was no change reported in experienced coercion in the past month among YFSW (7.6% vs 4.6%, p = 0.180).

10.1371/journal.pone.0288717.t002 Change in practice of sex work and context in the early and recent period of sex work among young female sex workers in Mombasa, Kenya, 2015.
  Early (N = 408) % Recent (N = 408) % P value
Management of sex work Pimp 6.4 1.5 <0.001
Manager 4.4 1.5
Self-managed 91.2 98.0
Number of paying clients per week 0–2 46.2 39.3 <0.001
3–4 34.1 19.5
5 or more 16.5 39.3
Do not know/ did not answer 3.2 1.9
Mean number of paying clients per week (#) 4.0 client (SD†-8.3) 5.7 client (SD†-6.9) <0.001
Meet living expenses through income of sex work Less than half 30.2 15.0 <0.001
Half 51.0 38.2
More than half 18.8 46.8
Experienced coercion in the past month 7.6 4.6 0.18
Experienced police violence in the past month 6.5 16.4 <0.001

†SD: Standard deviation

Table 3 shows the change in typology from the early to recent period of sex work with an increase in the proportion of YFSW reporting using internet and mobile phone (4.9% to 19.1%, p<0.001). However, no major changes were reported in the use of street and bus stops (45.6% to 40.2%, p = 0.119); entertainment venues (70.6% to 75.5%, p = 0.115); hotel and lodges (21.6% to 25.7%, p = 0.168), and other (40.7% to 35.8%, p = 0.150) typology of sex work between early and recent period.

10.1371/journal.pone.0288717.t003 Distribution in typology in early and recent period of sex work among young female sex workers, Mombasa, Kenya, 2015.
Typology of sex work† Early N = 408 Recent N = 408 P Value
Internet/Mobile phone 4.9% 19.1% 0.001
Street/Bus stop 45.6% 40.2% 0.119
Entertainment venue 70.6% 75.5% 0.115
Hotel/Lodge 21.6% 25.7% 0.168
Others 40.7% 35.8% 0.150

†Typology of sex work here is defined as multiple options and all the different typologies solicited in the respective period.

 Change in extent and pattern of overlap of typology of sex work

Fig 1 (panel A and B) shows that at both the early and recent periods of sex work, YFSW used more than one sex work typology. In the early period of sex work, 100% of the internet and mobile phone based, 80.1% of street and bus stop based, 64.7% of entertainment based, 88.6% hotel and lodge based and 80.1% YFSW practicing in other typology of sex work also practiced in more than 2 other typologies. Similarly, at the recent period of sex work, 94.7% of the internet and mobile phone based, 81.1% of street and bus stop based, 71.8% of entertainment based, 71.5% hotel and lodge based and 71.5% FSW practicing in other typology of sex work also practiced in more than 2 other typologies.

10.1371/journal.pone.0288717.g001 Change in extent and pattern of overlap of typology of sex work between the early and recent period of sex work among young female sex workers in Mombasa, Kenya, 2015.

Fig 1 (panel C and D) shows that in the early and recent periods of sex work, most of the overlap in typologies were in entertainment venues. In the early period of sex work, 55.0% of YFSW from internet and phone-based typology, 65.1% from the street and bus stop typology, 76.1% from hotel and lodge typology and 59.6% from other typology also used entertainment venues. However, in the recent period, there was an increase in the overlap with entertainment venues. 85.9% of YFSW from internet and phone-based typology, 69.5% from the street and bus stop typology, 81.9% from hotel and lodge typology and 64.4% from other typology also used entertainment venues. The overall pattern of overlap in typologies changed between the early and recent period of sex work, with higher overlap with entertainment venues during the recent period of sex work.

 Pattern of within person change in primary typology of sex work

Overall, 37.2% (150/403) of the respondents reported changing their primary typology of sex work between their early and recent period of sex work. There was not much variation in change in primary typology of sex work by duration in sex work (S2 Table). Fig 2 shares within person change in primary typology between the early and recent period of sex work. Among those who changed primary typology, in the early period, 1.3% of the respondents reported being internet and mobile phone based, 38.0% street and bus stop based, 36.0% entertainment venue based, 5.3% hotel and lodge based and 19.3% reported other typologies of sex work. A shift was noticed among YFSW in all typologies as 80.7% of those street/bus stop based in the early period shifted to entertainment venues and another 14.0% shifted to other typologies. Among YFSW in entertainment venues in the early period, 24.1% shifted to internet/mobile phone, 29.6% shifted to street/bus stop, 18.5% shifted to hotel/lodge and the remaining 27.8% shifted to other typology of sex work. Similarly, from the hotel/lodge-based sex worker, 37.5% shifted to entertainment venues and the remaining 62.5% shifted to other typology of sex work. Among those in other typologies in the first month, a very large proportion shifted to entertainment venue (82.8%), and very few to street/bus stop (6.9%) and hotel/lodges (6.9%). These changes therefore contributed to a change in primary typology in the recent period as 10.0%, 12.7%, 49.3%, 8.0% and 20.0% reported their primary typology as internet and mobile phone based, street/bus stop based, entertainment venue based, hotel/lodge based and other typologies respectively.

10.1371/journal.pone.0288717.g002 Pattern of within person change in primary typology of sex work between the early and recent period of sex work among young female sex workers who changed their primary typology in Mombasa, Kenya, 2015. Characteristics of YFSW in the early period among those who changed their primary typology

Table 4 shows the characteristics in the early period of sex work for YFSW who changed their primary typology. Compared to those who did not change their primary typology, a higher proportion of YFSW who changed their primary typology were street and bus stop based (18.2% vs. 38.0%, p<0.001), experienced police violence in the past month (4.7% vs. 9.7%, p = 0.05) and initiated sex work after 19 years of age (33.3% vs. 45.3%, p<0.02).

10.1371/journal.pone.0288717.t004 Characteristics of young female sex workers at early period of sex work, who changed their primary typology of sex work between early and recent period of sex work, Mombasa, Kenya, 2015.
  First month of sex work
Total Change of typology P Value
Changed Not Changed
  N = 408 n = 150 n = 258
Primary typology Internet/mobile phone 0.5 1.3 0.0 <0.001
Street/bus top 25.5 38.0 18.2  
Entertainment venue 53.7 36.0 64.0  
Hotel lodge 4.9 5.3 4.7  
Others 15.4 19.3 13.2  
Management of sex work Pimp 6.4 8.0 5.4 0.27
Manager 4.4 6.0 3.5  
Self 91.2 90.0 91.8  
Meet living expenses through income of sex work Less than half 30.2 35.1 27.3 0.21
Half 51.0 45.9 53.9  
More than half 18.8 18.9 18.8  
Number of paying clients per week† <3 47.7 50.7 46.0 0.60
3–4 35.2 32.1 36.9  
5+ 17.1 17.1 17.1  
 
  Mean number of paying clients in the first month of sex work 4.0 4.2 3.9 0.51 
Percent experienced physical violence in the past month   5.0 6.2 4.4 0.42
Percent experienced coercion in the past month   4.6 2.1 6.0 0.07
Percent experienced police violence in the past month   6.5 9.7 4.7 0.05
Left Home/ living with parents Left home 61.8 57.3 64.3 0.16
Living with parents/others 38.2 42.7 35.7
Age at start of sex work < = 15 years 19.1 13.5 22.4 0.02
16–18 years 43.2 41.2 44.3
19+ years 37.7 45.3 33.3
Mean age at start of sex work 18.0 18.0 17.0 0.04

† There were 16 respondents who did not remember or answer the number of paying clients in the early period

 Change in programme outcomes among YFSW who changed their primary typology

In terms of programme outcomes, Table 5 shows that overall 14.7% YFSWs were ever contacted by a peer/staff from NGO/CBO/FBO; 77.4% ever tested for HIV; and 13.7% ever visited a clinic run by NGO/CBO/FBO. Further, 7.3% tested positive for HIV. The Odds Ratio and Confidence Intervals shows that there was no difference in prevalent HIV infection, programme reach, utilization of services among YFSW who changed their primary typology of sex work compared to those who did not change.

10.1371/journal.pone.0288717.t005 Change in outcomes among young female sex workers who changed their primary typology of sex work between early and recent period of sex work compared to those who did not change, Mombasa, Kenya, 2015.
Outcomes Overall Percent Changed typology Exp (B) 95% CI for Exp (B) p
Lower Upper
Ever contacted by a peer/staff from NGO/CBO/FBO 14.7 (N = 402) No 1.000      
Yes 0.962 0.534 1.734 0.898
Ever tested for HIV 77.4 (N = 372) No 1.000      
Yes 1.105 0.664 1.839 0.702
Ever used a clinic run by NGO, CBO or FBO 13.7 (N = 408) No 1.000      
Yes 0.883 0.493 1.581 0.676
HIV prevalence 7.3 (N = 317) No 1.000      
Yes 0.671 0.268 1.682 0.395
Discussion

To the best of our knowledge, this is one of the first studies to focus on changes in sex work context, setting and practices within the early and recent period of sex work among YFSW in Kenya. Our findings show that even at the early period of sex work, there was a sub population of YFSW who were managed by third parties, had more than 5 paying clients, were meeting more than half of their living expenses through sex work and experienced police violence in the past month. Respondents reported an increase in self-management of their work, number of paying clients, meeting living expenses through the income of sex work and experiencing police violence by the recent period of sex work. In terms of typology, use of internet and mobile phone-based sex work increased from the early to the recent period of sex work. YFSW used more than one typology for sex work during both the early and recent period of sex work. The overlap in typology was high during both the periods of sex work with high overlap of entertainment venues among YFSW in all typologies of sex work. One third of YFSW changed their primary typology of sex work from the early to the recent period. Early sex work factors associated with change in primary typology were, street/ bus stop based sex work, experience of police violence and entry into sex work after 19 years. For YFSW, programme reach and service utilisation was low and prevalent HIV infection was moderately high at the early period of sex work. However, a change in primary typology by the respondents did not seem to change these outcomes among YFSW.

The ways in which sex workers operate continuously change, sometimes in response to contextual factors [17]. In a study conducted in Bangalore, India, changes related to age at initiation into sex work, type of partnerships, typology and setting of sex work and mobility of sex workers were noted over time [3]. Our study also shows that there were changes in sex work practices related to management, client volume, sex work income and police violence between the early and recent period of sex work. Self-management and autonomy impact a sex workers ability and freedom to negotiate condom use or regulate the number and type of clients [9] and higher sex work income is associated with consistent condom use with new clients among sex workers [41]. A systematic review conducted to understand the correlates of violence found evidence of the role of the work environment in shaping risks for violence among sex workers, with sex workers in street or public-place environments at highest risk of violence [42]. Another study conducted in India, also reported high violence in the first month of sex work [43]. While among YFSW, longer time in sex work may improve autonomy and income, however, the increase in the number of paying clients and police violence may also increase HIV related risks [44, 45]. It needs to be noted that even in the early period of sex work, a small sub population of YFSW respondents were managed by third parties, had high client volume and high violence. Programmes for YFSW in Mombasa, Kenya need to prioritise this subpopulation during the early period of sex work.

Buzdugan and colleagues in their paper describe that the sex work industry is very fluid and new settings emerge over time [9]. Ward et al in their longitudinal study of 15 years with FSW in London found that almost a third of them had worked in all typologies of sex work [5]. Matolcsi et al also found that the breadth of the sex industry is large and individuals are often involved in more than one typology or setting over time or concurrently [46]. In our study a higher proportion of respondents reported using multiple typologies in a shorter span of time, possibly a specific feature related to YFSW or Mombasa County. Entertainment venues were most popular among YFSW and would be an important site for interventions for programmes with YFSW in Mombasa. It is important to understand the interconnectedness between typologies and devise interventions at community and facility level that can maintain consistency in services across different typologies for all YFSW. Our findings also add to the body of emerging evidence that internet and cell phone-based sex work has increased globally [47]. Mahapatra et al found that use of cell phone among FSW was associated with increased HIV risk behaviors, independent of their place of solicitation [48]. With the increase in use of technology and cell phone in the lives of YFSW, interventions could devise technological and other solutions to reach individual YFSW on a regular basis irrespective of the typologies that they practice in [49].

In this study, we also found that a higher proportion of YFSW who changed their primary typology were street and bus stop based, experienced police violence in the past month and initiated sex work after 19 years of age at the early period of sex work. Programmes with YFSW should prioirtise reaching out to YFSWs with these characteristics with tailored interventions to provide support during the changes. Hendrickson et al also found in their study in Tanzania, that recently mobile FSW had a 25% increased risk of any recent experience of physical or sexual gender-based violence when compared with their non-mobile counterparts [50]. Though our study, in comparison, did not find any increased prevalent HIV incidence or decreased programme reach and service utilisation among YFSW who changed their primary typology of sex work, in general low programme reach and service utilisation and moderately high prevalent HIV incidence among the YFSW is very concerning and points towards the need to scale up HIV prevention programming with YFSW. Neufeld et al found that a large proportion of prevalent HIV infection among YFSW can be traced back to acquisition prior to entry into formal sex work. HIV prevention efforts targeting FSWs might overlook the opportunity to prevent HIV among the younger population if interventions fail to reach them early in their sexual life course [51].

Future research could focus on understanding risk and vulnerability linked to each typology to develop focused interventions to specifically target these typologies for YFSW. This information should also inform programmatic mapping and key population size estimation exercises to account for mobility of YFSW across sites [52]. Intervention models should be tested to explore feasibility of individualized outreach and service provision through use of technology. Future research should also focus on enhanced understanding of change in typology–who is changing, why are they changing, how does it impact programme reach etc.

Limitations

The study examined the change in typology and its relationship with the sex work practices and contexts. First, we used the primary typology in the early and recent period to assess the change in typology. YFSWs might have changed their typologies between the period of early and recent periods and then shifted back to the early period typology in the recent period. However, we expect that these could be a small proportion, if any, considering the median duration in sex work was 2 years. Further, we present the different typologies of sex work that the respondents practiced in the early and recent periods separately, and show the overlap of typologies within and between periods. Secondly, the study retrospectively asked the sex work practices and contexts in the early period. There could be potential recall lapse, however, considering the short duration between early and recently period (median = 2 years) and since almost all of the respondents responded to the question, we consider such recall lapse is unlikely or minimum. Thirdly, the study sampled from the physical hotspots and hence may have left out respondents who seek clients and partners exclusively using the internet.

 Conclusions

YFSW change their sex work practices and typology of sex work within a short period of time. Understanding these changes in the early period of sex work could be important to design effective HIV prevention interventions to reach YFSW. Given global acknowledgement of the need to scale up interventions with YFSW, this paper provides new information that should be considered while designing and implementing interventions with YFSW.

 Supporting information List of questions.

(DOCX)

 Change in primary typology of sex worker by duration of sex work among young female sex workers in Mombasa, Kenya 2015.

(DOCX)

 Inclusivity in global research.

(DOCX)

We thank the study participants and the research team involved in data collection in Mombasa. We thank the other members of the Transition Study Team including James Blanchard (University of Manitoba), Stephen Moses (University of Manitoba), Marie-Claude Boily (Imperial College London), Michael Pickles (Imperial College London), Daria Pavlova (Ukrainian Institute for Social Research After Oleksandr Yaremenko), Olga Balakireva (Ukrainian Institute for Social Research After Oleksandr Yaremenko), Larry Gelmon (University of Manitoba), Joshua Kimani (University of Manitoba), Fridah Muinde (National Syndemic Diseases Control Council), Martin Wafula Sirengo (National AIDS and STI Control Programme), Reynold Washington (India Health Action Trust), Sevgi Aral (Center for Disease Control), Lyle McKinnon (University of Manitoba), Yoav Keynan (University of Manitoba), Keith Fowke (University of Manitoba), Paul Sandstorm (University of Manitoba) and Eve Cheuk (University of Manitoba).

 Abbreviations YFSW

Young Female Sex Worker

 FSW

Female Sex Workers

 STI

Sexually Transmitted Infections

 NGO

Non-Governmental Organisation

 FBO

Faith based Organisation

 CBO

Community based Organisation

 OR

Odds Ratio

 CI

Confidence Interval

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Programmatic mapping: providing evidence for high impact HIV prevention programs for female sex workers. JMIR Public Health Surveill. 2019;5(2):e12636 doi: 10.2196/12636 31172964 10.1371/journal.pone.0288717.r001 Decision Letter 0 Blumenthal Jill Academic Editor 2023 Jill Blumenthal This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Submission Version 0

3 Apr 2023

PONE-D-22-24072Variability in the context between early and recent periods of sex work among young female sex workers in Mombasa, Kenya: a cross-sectional studyPLOS ONE

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Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: In the manuscript “Variability in the context between early and recent periods of sex work among young female sex workers in Mombasa, Kenya: a cross-sectional study,” authors use data from a 2015 cross-sectional survey with 408 female sex workers to assess differences in context and practices of sex work between the first month of the woman’s engagement in sex work and more recent sex work because differences may implicate a need for different time-period tailored HIV prevention programs. While the research question is important and study has potential for high impact, it has several shortcomings which need to be addressed.

Abstract: Consider briefly defining ‘typology’ and ‘early’ vs. ‘recent’ as these terms are not readily apparent/familiar to readers who do not commonly conduct research/programs with this population. The Results statement beginning with “higher proportion among street/bus stop typology” seems incomplete and should be reworded for clarity.

Intro: For clarity, consider defining “early” vs “recent” period and age criteria for “YFSW” early on in the intro (i.e., at first reference). Also, consider expanding on the hypothesis that HIV/STI risk may vary by change in typology and sex work practices over time. Why and how might change in typology and sex practices change HIV risk? Why/how this could impact HIV prevention strategies? This will further justify research question and need for the study.

Methods:

- As a key aim of the study is to assess change in typology of sex work over time, how adequate were current recruitment methods in comprehensively identifying/recruiting participants across dimensions of typology? i.e., if participants were recruited from sex work venues, would participant who engaged in home-based or internet-based sex work be adequately identified? The period of “early” vs. “recent” could have different impact based on how long the participant had been involved with sex work. For example, we might expect little variation in someone who had only been employed for 2 months vs 24 months in sex work. How was this handled?

- Were participants reimbursed for participation? What was the length of the survey? How was the privacy and safety of the participants ensured?

- More details regarding how the predictors “physical violence,” “experience of coercion,” and “living condition” were assessed and analyzed is needed.

- The study outcomes should be identified and defined consistently. For example, lines 151-152 describe planned assessment of the impact of primary typology on “HIV prevalence” and “program reach.” Is prevalence the right outcome? Perhaps HIV status (negative vs. positive) is more appropriate? How is program reach defined and measured? The Statistical Analysis section only discusses testing the association between change in primary typology and factors associated with change in typology. This is discrepant from the prior section.

Results:

- Table 1 should depict the spread of values for individuals engaged in sex work <2 years.

- Table 2 should include physical violence and living condition as described in the Methods

- Table 3 text should describe overlap between typologies. How is this handled/depicted in the table?

- A key is needed to explain shading in Figure 1

- Table 4 and 5 don’t seem to be hypothesis driven or aligned with the paper. For example, the analysis presented answers what factors drove change in typology and impact of change in typology on outcome. I think the real question that authors are interested in is the switch from a lower-risk to a higher-risk typology and this is not being assessed in the current analysis.

Overall comments: The manuscript could benefit from grammar/spelling proofing.

Reviewer #2: Thank you for the opportunity to review this interesting study. The authors aim to assess changes in the context and typology of sex work across early and recent phases of sex work and implications for HIV programmes. Strengths include the peer-led nature of data collection and the potential significance of addressing this more nuanced aspect of sex work, which is a gap in the literature. However, there are a number of substantial methodologic issues and questions that I would recommend be addressed to support rigor and clarity of this work and its potential contribution to the literature. Below I've identified some point-by-point questions and comments for the authors to consider. Additionally, there are considerable language and grammatical issues that require addressing for the manuscript to be fully intelligible and clear.

Abstract & Title

1. The relevance of this work is not quite clear based on the current framing of the title and introduction.

2. More clarity regarding which programmes are being referred to and why they would only be focusing on 'several years' after entry into sex work is unclear from the abstract.

3. The title and objective would benefit from more unpacking and clarity, especially as the study relates to HIV or other health outcomes.

4. The conclusions provided in the abstract are fairly vague and would benefit from more specific recommendations and clarity.

Introduction

5. The introduction would be strengthened by revising the opening paragraph to provide more nuance and clarity regarding the broader study context and justification - why do typologies of sex work and changes over time matter, and how could this information be used in HIV or other health programming would ideally be clearer much earlier in the paragraph.

6. Some awkward terms are used (eg, scanty) that should be addressed, and much of the description of concepts (eg, which 'programmes' are being referred to in the first sentence? what is meant by 'critical outcomes' in the objective??) is vague, leaving the reader wondering exactly what is meant. More precise language and clarification of key concepts would strengthen the introduction and all sections of the manuscript. The hypotheses for the study also require clarification.

Methods

7. The sole reliance on descriptive methods is a substantial methodologic weakness. I appreciate the descriptive analysis, but wonder why no odds or risk ratios (bivariate) were provided? ORs/RRs and 95% CIs could provide more nuanced effect estimates and interpretation over sole reliance on p-values and comparing percentages. Additionally, a more focused analysis that includes multivariable modeling to adjust for confounding may provide a stronger study design and weight of evidence.

Results

8. The authors may consider referring to pimps/managers as 'third parties' as this is a more neutral term that describes these types of sex industry roles, that may help avoid the stigma, myths and misconceptions that are often attributed to social norms surrounding 'pimps' and their role in sex transactions.

9. There is a large amount of descriptive data provided, and inclusion of more bivariate effect sizes and 95% CIs, as well as some multivariable modeling addressing key hypotheses and relationships between variables, could provide a stronger set of results.

**********

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Reviewer #1: No

Reviewer #2: No

**********

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Submitted filename: PLOSONE.docx

 10.1371/journal.pone.0288717.r002 Author response to Decision Letter 0 Submission Version 1

15 Jun 2023

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We have now included the PLOS’ questionnaire on inclusivity in global research as supporting information (S1File). We have also included a subsection ‘Inclusivity in global research’ to your Methods section (page 11, Line 213-214)

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The participants for the study included adolescent girls and young women from 14 to 24 years congregating at sex work hotspots. The local IRB waived the need for parental consent. We have now included the same in the Methods section (page 7 Line 134-137).

4. Thank you for stating in your Funding Statement:

“MB, SM were supported by CIHR grants - MOP 13044 and FDN13455. PB was supported by BMGF grant - INV006613. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.”

Please provide an amended statement that declares *all* the funding or sources of support (whether external or internal to your organization) received during this study, as detailed online in our guide for authors at http://journals.plos.org/plosone/s/submit-now. Please also include the statement “There was no additional external funding received for this study.” in your updated Funding Statement.

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We have revised the funding statement in the manuscript and has also included the same in our cover letter

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“We thank the study participants and the research team involved in data collection in Mombasa. The study was funded by an operating grant (MOP-13044) from the Canadian Institutes of Health Research (CIHR) and analyses funded via CIHR grant FDN 13455. Analysis for this manuscript was also supported by the Bill & Melinda Gates Foundation (BMGF) under grant INV-006613. The views expressed herein are those of the authors and do not necessarily reflect the official policy or position of the funders. “

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Please remove any funding-related text from the manuscript and let us know how you would like to update your Funding Statement. Currently, your Funding Statement reads as follows:

“MB, SM were supported by CIHR grants - MOP 13044 and FDN13455. PB was supported by BMGF grant - INV006613. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.”

Please include your amended statements within your cover letter; we will change the online submission form on your behalf.

We have now revised the acknowledgement section (page 21, lines 427- 458) and the funding statement (cover letter).

6. One of the noted authors is a group or consortium [The Transitions Team]. In addition to naming the author group, please list the individual authors and affiliations within this group in the acknowledgments section of your manuscript. Please also indicate clearly a lead author for this group along with a contact email address.

We have now added names of other Transitions Team members and their affiliations in the acknowledgement (page 21, lines 427-458). We have also added the name of the lead author and the contact email (page 2, lines 29-30).

7. Please include your tables as part of your main manuscript and remove the individual files. Please note that supplementary tables (should remain/ be uploaded) as separate "supporting information" files

We have added the tables as part of the main manuscript (pages 26-29) and have added the supplementary table as separate supporting information files (S1 Table, S2 Table and S1 File).

Additional Editor Comments (if provided):

The second reviewer points out several methodologic issues that need to be addressed to support this work and lead to publication.

We appreciate the comments of the second reviewer. We have made revisions as best as we could. We have, in particular, based on reviewers’ feedback, added Odds Ration and 95% confidence interval along with p values in Table 5 (page 29) to provide nuanced analysis. However this is a descriptive paper and the analysis is used to describe the changes in sex work practices, context, typologies and primary typology of sex work during the early and recent periods of sex work, in Mombasa, Kenya and therefore the scope of the paper is not to predict risk. This descriptive analysis has been done to inform programme planning and implementation. We acknowledge the limitations of a descriptive analysis and have made revisions as best as we can to address the concerns of the second reviewer. However, we contend that a descriptive analysis also provides an important set of new findings, as recently noted by Platt and Lesko et al. We have cited this framework for descriptive epidemiology in our revised manuscript.

Reviewers' comments:

Reviewer #1: In the manuscript “Variability in the context between early and recent periods of sex work among young female sex workers in Mombasa, Kenya: a cross-sectional study,” authors use data from a 2015 cross-sectional survey with 408 female sex workers to assess differences in context and practices of sex work between the first month of the woman’s engagement in sex work and more recent sex work because differences may implicate a need for different time-period tailored HIV prevention programs. While the research question is important and study has potential for high impact, it has several shortcomings which need to be addressed.

1. Abstract: Consider briefly defining ‘typology’ and ‘early’ vs. ‘recent’ as these terms are not readily apparent/familiar to readers who do not commonly conduct research/programs with this population. The Results statement beginning with “higher proportion among street/bus stop typology” seems incomplete and should be reworded for clarity.

Thank you for the feedback. In the revised manuscript we have defined the terms typology, early and recent more clearly in the abstract and have also revised the result statement (page 3, lines 42, 48).

2. Intro: For clarity, consider defining “early” vs “recent” period and age criteria for “YFSW” early on in the intro (i.e., at first reference). Also, consider expanding on the hypothesis that HIV/STI risk may vary by change in typology and sex work practices over time. Why and how might change in typology and sex practices change HIV risk? Why/how this could impact HIV prevention strategies? This will further justify research question and need for the study.

Thank you very much for the comments. In the introduction, we have defined the key words at the first reference. We have also added new evidence to show the variation in HIV and STI risk by sex work typology and why change in typology may facilitate HIV risk among FSW. We hope that this will justify the need to understand change in typology and sex work practices for improved prevention programming (pages 5-6, lines 72-115).

2. Methods:

- As a key aim of the study is to assess change in typology of sex work over time, how adequate were current recruitment methods in comprehensively identifying/recruiting participants across dimensions of typology? i.e., if participants were recruited from sex work venues, would participant who engaged in home-based or internet-based sex work be adequately identified? The period of “early” vs. “recent” could have different impact based on how long the participant had been involved with sex work. For example, we might expect little variation in someone who had only been employed for 2 months vs 24 months in sex work. How was this handled?

- Were participants reimbursed for participation? What was the length of the survey? How was the privacy and safety of the participants ensured?

Thank you for the comment. The study started with mapping of physical locations where female sex workers congregated to solicit clients and/or where sex work-related sexual activities took place. The method and the results of the mapping exercise is described in a paper written by our Transitions study team member. We have also added this reference in the method section (page 8, line 140). The recruitment method for this study sampled only physical hotspots identified during the mapping exercise which included local brew dens, night clubs, sex den, bars with and without lodging, brothels, streets, public spaces, guesthouses, restaurant, massage parlours, truck stops, video dens and homes. Hence, the sampling approach adopted for the study represented all physical sites, including homes. However, the study did not sample virtual sites and would have left out respondents exclusively using internet. We have now included this exclusion as a limitation of the study (Page 19, lines 404-405).

We agree that the period of “early” vs. “recent” could have different impact on change in primary typology based on how long the participant had been involved with sex work. However, we did not find a variation by duration in sex work and change in typology as defined in years (even when we considered less than 6 months when it was less than 1 year). Therefore, we presented this in years in the table and did not break into many categories considering the sample size in each cells. We did however, as suggested, conduct a sensitivity analysis. The change in primary typology by years in sex work (in months for below 1 year, 1-2 years, 3-4 years and above 5 years is presented now as supporting information in the paper (S2 Table).

The participants were reimbursed Ksh 850 (USD 10) for their time. The actual survey took 1hour and 30 minutes including the collection of biological samples. The survey took place in private spaces that were identified by the study team. The spaces were located within the Drop-in Centres and clinics managed by our local partner, International Centre for Reproductive Health – Kenya (ICRH-K) or government clinics identified by the peer educators as safe and friendly spaces. All the rooms where the face-to-face interviews and biological sample collections took place had privacy for the respondents. All respondents were given a unique ID to protect confidentiality and this ID was attached to their questionnaire and biological sample. Hard copies of the filled questionnaires and other documents were stored in locked cabinets, accessible only by members of the research team. The electronic data was entered in a password protected computer and stored in a password protected server. Only the research team had access to the data (page 8, lines 150-159).

- More details regarding how the predictors “physical violence,” “experience of coercion,” and “living condition” were assessed and analyzed is needed.

Thank you so much for your comment. We have now added a supporting information table sharing relevant questions that were used to define the variables (S1 Table). This will help readers understand how the variables used in the analysis were defined.

- The study outcomes should be identified and defined consistently. For example, lines 151-152 describe planned assessment of the impact of primary typology on “HIV prevalence” and “program reach.” Is prevalence the right outcome? Perhaps HIV status (negative vs. positive) is more appropriate? How is program reach defined and measured? The Statistical Analysis section only discusses testing the association between change in primary typology and factors associated with change in typology. This is discrepant from the prior section.

Thank you so much for the comment. We have now renamed the HIV prevalence outcome as prevalent HIV infection starting from introduction section (page 7, line 124) and then used consistently throughout the rest of the manuscript. We have now defined programme reach and service utilisation in the methods section (page 10-11, lines 189 -193) and also revised the statistical analysis section to include the outcomes (page 10, 206-209).

3. Results:

- Table 1 should depict the spread of values for individuals engaged in sex work <2 years.

We have now revised Table 1 to show the spread of values for respondents engaged in sex work < 2 years (page 26).

- Table 2 should include physical violence and living condition as described in the Methods

Thank you for your comment. We have added supplementary information describing the questions used to define these variables (S1 Table).

- Table 3 text should describe overlap between typologies. How is this handled/depicted in the table?

Thank you for your comment. We apologise for the confusion created. Table 3 describes the distribution in typology in the early and recent period of sex work among young female sex workers. We have revised the title of the table (page 27) for greater clarity. The table does not describe overlap. Overlap is described in Figure 1.

- A key is needed to explain shading in Figure 1

Thank you for the comment. The key has been added to Figure 1 now.

- Table 4 and 5 don’t seem to be hypothesis driven or aligned with the paper. For example, the analysis presented answers what factors drove change in typology and impact of change in typology on outcome. I think the real question that authors are interested in is the switch from a lower-risk to a higher-risk typology and this is not being assessed in the current analysis.

Thank you for your question. We have clarified that our study cannot answer the question surrounding whether switching from a lower risk to higher risk typology has occurred. Rather, we aimed to describe if differences in primary typology were associated with prevalent HIV infection (Table 5) (page 29). For Table 4 (page 28), our focus was solely on describing the characteristics of those who reported a change in their primary typology, and not testing a hypothesis. We have revised the manuscript to clarify the descriptive nature of the study (page 10, lines 198 -203).

4. Overall comments: The manuscript could benefit from grammar/spelling proofing.

Thank you for the comment. We have done a grammar and spelling proof of the manuscript.

Reviewer #2: Thank you for the opportunity to review this interesting study. The authors aim to assess changes in the context and typology of sex work across early and recent phases of sex work and implications for HIV programmes. Strengths include the peer-led nature of data collection and the potential significance of addressing this more nuanced aspect of sex work, which is a gap in the literature. However, there are a number of substantial methodologic issues and questions that I would recommend be addressed to support rigor and clarity of this work and its potential contribution to the literature. Below I've identified some point-by-point questions and comments for the authors to consider. Additionally, there are considerable language and grammatical issues that require addressing for the manuscript to be fully intelligible and clear.

5. Abstract & Title

5.1 The relevance of this work is not quite clear based on the current framing of the title and introduction.

Thank you for the feedback. We have changed the title (page 1, lines 1-2) and the abstract to clearly communicate the objective of the study and its relevance.

5.2. More clarity regarding which programmes are being referred to and why they would only be focusing on 'several years' after entry into sex work is unclear from the abstract.

Thank you for the feedback. We have clarified that we are referring to HIV prevention programmes with female sex workers when we refer to ‘programmes’. The HIV prevention programmes with female sex workers reach female sex workers several years after they self-identify as sex workers. Considering prevalent HIV incidence among young female sex workers, we feel that there is need to understand the context and setting in the early years of sex work to design HIV prevention programmes with young female sex workers to ensure early reach and access.

.

5.3. The title and objective would benefit from more unpacking and clarity, especially as the study relates to HIV or other health outcomes.

Thank you for your feedback. We have revised the title to now relate more with the study objectives (page 1, lines 1-2). The study relates to HIV related outcomes rather than broader health outcomes. We have clarified this point throughout the paper.

5.4. The conclusions provided in the abstract are fairly vague and would benefit from more specific recommendations and clarity.

Thank you for the feedback. We have revised the conclusions to provide clear recommendations based on the study findings (page 4, lines 66-68)

6. Introduction

6.1. The introduction would be strengthened by revising the opening paragraph to provide more nuance and clarity regarding the broader study context and justification - why do typologies of sex work and changes over time matter, and how could this information be used in HIV or other health programming would ideally be clearer much earlier in the paragraph.

6.2 Some awkward terms are used (eg, scanty) that should be addressed, and much of the description of concepts (eg, which 'programmes' are being referred to in the first sentence? what is meant by 'critical outcomes' in the objective??) is vague, leaving the reader wondering exactly what is meant. More precise language and clarification of key concepts would strengthen the introduction and all sections of the manuscript. The hypotheses for the study also require clarification.

The introduction section has been edited extensively to incorporate the reviewers feedback and suggestions (pages 5-6, lines 72-115).

7. Methods

7.1 The sole reliance on descriptive methods is a substantial methodologic weakness. I appreciate the descriptive analysis, but wonder why no odds or risk ratios (bivariate) were provided? ORs/RRs and 95% CIs could provide more nuanced effect estimates and interpretation over sole reliance on p-values and comparing percentages. Additionally, a more focused analysis that includes multivariable modeling to adjust for confounding may provide a stronger study design and weight of evidence.

We are thankful for your feedback. In particular, based on the reviewers’ feedback, we have now added Odds Ratio and 95% confidence interval along with p values in Table 5 (page 30). The scope of the paper is to look at patterns rather than predict risk and hence we used descriptive analysis. This descriptive analysis has been done to inform programme planning and implementation. We acknowledge the limitations of a descriptive analysis and have made revisions as best as we can to address the concerns of the second reviewer. However, we contend that a descriptive analysis also provides an important set of new findings, as recently noted by Platt and Lesko et al. We have cited this framework for descriptive epidemiology in our revised manuscript (page 10, lines 198- 200).

8.Results

8.1 The authors may consider referring to pimps/managers as 'third parties' as this is a more neutral term that describes these types of sex industry roles, that may help avoid the stigma, myths and misconceptions that are often attributed to social norms surrounding 'pimps' and their role in sex transactions.

Thank you so much for the feedback. In the paper narrative we have replaced pimps/ managers as third parties (page 16, line 315 and page 17, line 346).

8.2. There is a large amount of descriptive data provided, and inclusion of more bivariate effect sizes and 95% CIs, as well as some multivariable modeling addressing key hypotheses and relationships between variables, could provide a stronger set of results.

Thank you for this comment. Based on your feedback we have added Odds Ratio and 95% Confidence Interval in Table 5 (page 29). However, we would like to affirm that this is a descriptive paper and the analysis is used to describe the changes in sex work practices, typologies and primary typology of sex work during the early and recent periods of sex work, in Mombasa Kenya. We then characterize those young female sex workers who change their primary typology, and assess the impact of this change on critical outcomes. This descriptive analysis has been done to inform program planning and implementation. We note that you appreciate the descriptive analysis.

Submitted filename: Response to reviewers, 15th June 2023.docx

 10.1371/journal.pone.0288717.r003 Decision Letter 1 Blumenthal Jill Academic Editor 2023 Jill Blumenthal This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Submission Version 1

5 Jul 2023

Changes in context, typology and programme outcomes between early and recent periods of sex work among young female sex workers in Mombasa, Kenya: a cross-sectional study

PONE-D-22-24072R1

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Additional Editor Comments (optional):

We appreciate your attention to the responses offered and have no further recommended edits.

 10.1371/journal.pone.0288717.r004 Acceptance letter Blumenthal Jill Academic Editor 2023 Jill Blumenthal This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

17 Jul 2023

PONE-D-22-24072R1

Changes in context, typology and programme outcomes between early and recent periods of sex work among young female sex workers in Mombasa, Kenya: a cross-sectional study

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