Nurse counselors’ experiences of recruitment and retention of female sex workers in a HIV vaccine trial: a qualitative study from urban Tanzania

Abstract

Background

Nurse counselors play a pivotal role in recruiting and facilitating the retention of volunteers in HIV vaccine trials. They act as the primary interface between the research team and volunteers, typically tasked with educating, supporting, and guiding participants through the trial process, including adherence to the study protocol for care and safety. There is limited research on the series of experiences and challenges faced by nurse counselors during the recruitment and retention of volunteers in HIV vaccine trials. This study aimed to describe the experiences of nurse counselors in recruiting and retaining female sex workers in the HIV PrEP and Vaccine (PrEPVacc) trial.

Methods

This employed a descriptive qualitative study design nested within the larger phase IIb three-arm, two-stage HIV prophylactic vaccine trial conducted in Dar es Salaam, Tanzania. The qualitative data were collected among three nurse counselors and one field worker who participated in 16 debrief sessions. The participants were purposefully selected due to their roles and responsibilities in the recruitment and retention of volunteers. The audio-recorded sessions were transcribed verbatim, and the content analysis approach was applied.

Findings

The study revealed that nurse counselors felt responsible and honored through enhancing volunteers’ recruitment and enrollment, ensuring retention, and facilitating trial interventions. The availability of a supportive trial environment, engagement meetings, collaboration among staff and volunteers, good staff performance, and volunteers’ positive attitude were the qualities for effective management of volunteers in the trial. However, the participants described encountering barriers to trial recruitment and retention, such as volunteers’ noncompliance with trial requirements, perceived lack of honesty, personal life and family resistance, stigma, and social perception.

Conclusion

The nurse counselors can encounter great turmoil while ensuring recruitment and retention in an HIV vaccine trial. Despite the challenges, volunteer engagement and adherence to study protocol are important for maintaining the continuity of trial procedures over time. Collaboration among staff and engagement of volunteers are essential to enhancing retention until the end of the study.

Trial registration

The trial was registered with the US clinicaltrials.gov on 29 September 2021 and can be found at https://clinicaltrials.gov/study/NCT04066881. Registration number: NCT04066881.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s13063-026-09835-9.

Background

Substantial improvements have been made in the fight against HIV/AIDS; however, the epidemic remains a conundrum as it is still incurable [1, 2]. Many of the advances made fall in the area of HIV/AIDS treatment due to the availability of highly effective antiretroviral therapy (ARV) [3], with prevention of the disease remaining a critical focus, including the search for an effective vaccine as a viable solution to the pandemic. The role of volunteers in conducting HIV vaccine trials cannot be overemphasized [4]. In conducting HIV vaccine studies, volunteers play a crucial and multifaceted role, mainly by advancing medical knowledge and giving crucial safety and efficacy data that cannot be obtained in any other means [5]. The key factors influencing recruitment and retention in HIV vaccine trials in Sub-Saharan Africa include perceived risks and benefits, social and community support systems [4, 6]. Both trial-related and participant-related factors impact the willingness to participate in a clinical trial [7]. Therefore, these factors warrant careful consideration to ensure the success of the trials.

One of the major challenges HIV vaccine trials implementers face is recruiting volunteers. Studies have highlighted issues such as stigma, mistrust in medical research, and the complexity of informed consent processes as significant obstacles [8]. Specifically, these challenges can be categorized as personal risks, including concerns about vaccine side effects; social risks, such as fear of discrimination due to false HIV positivity; personal costs, including requirements to avoid pregnancy and the time dedicated to the trial; social costs, such as family commitments; and misconceptions, like the belief that participants might be injected with HIV during the trial [9–12]. Understanding these challenges provides insights into improving the effectiveness of volunteer recruitment for future HIV vaccine trials, thereby increasing the potential for successful implementation of HIV vaccine trials.

Nurse counselors play a pivotal role in vaccine trials, including those focusing on the search for HIV, playing a significant role in recruiting and facilitating the retention of volunteers [13]. Thus, they often act as the primary interface between the research team and volunteers, usually tasked with educating, supporting, and guiding participants through the trial process, including ensuring dual fidelity to the protocol and participant care and safety [14, 15]. Given the role played by nurse counselors in complex clinical trials, it is clear that they significantly contribute to the integrity of such trials [14]. This positions them as crucial participants, serving as reliable sources of information regarding recruitment and the day-to-day dynamics of volunteers’ participation. The contribution of nurse counselor in the recruitment of vaccine trial participants has been widely documented [16, 17].

Despite their critical role, there is limited research on the experiences and challenges faced by nurse counselors in enrolling and retaining volunteers. Understanding these experiences is essential to improving recruitment strategies and providing better support to both nurse counselors and volunteers. However, the use of debriefs from the trial staff to complement the recruitment and retention has not been extensively studied. This study used structured debriefs to explore the experience of nurse counselors in recruiting and retaining FSWs in the HIV vaccine trial in Dar es Salaam, Tanzania.

Materials and methods

Design

This was a longitudinal qualitative study nested within a multicenter phase IIb three-arm, two-stage HIV prophylactic vaccine trial with a second randomization to compare TAF/FTC to TDF/FTC as pre-exposure prophylaxis (PrEPVacc). The qualitative study was conducted in the form of debriefs to explore the daily experiences and perceptions of providing education and counseling during the recruitment and retention of FSWs (volunteers) who were participating in the PrEPVacc trial. The study was guided by a pragmatic epistemological orientation, stressing the generation of contextually useful knowledge to address the research objective. While the qualitative design aimed at capturing participants’ accounts in their own terms, the analysis extends beyond surface description to interpret underlying meanings and relational dynamics. This approach was informed by an interpretivist orientation, which assumed that experiences of trial recruitment and retention are socially constructed and contextually negotiated. The qualitative was used due to its flexibility and dynamic nature that transforms the data beyond participants’ surface meaning [18]. We used the standard guideline for reporting qualitative research (SRQR) (Additional file 1).

Context, population, and recruitment

The study was conducted at the HIV vaccine trial unit at Muhimbili University of Health and Allied Sciences in Dar es Salaam, Tanzania. Three nurse counselors (one male and two females) and a field worker (female) were purposively selected to participate in a series of debriefing sessions to explore their daily experiences during the recruitment and retention of the volunteers in the HIV vaccine trial. Although female sex workers constituted the participant population of the trial, this study primarily focused on the perspectives of frontline trial staff involved in recruitment and follow-up activities. These actors were selected due to their direct involvement in implementing recruitment and retention procedures and their ongoing interaction with participants throughout the trial process. Both the nurse counselors and the field workers had the same role: recruiting and retaining the volunteers in the study. The trial took place between 2021 and 2023. Since this was longitudinal qualitative research, it allowed interaction and interplay with the collection and analysis of data for multiple points in time. Our goal was not just to find all themes at a single point, but to understand how themes, patterns, and their interrelationships evolved or remained stable across different time points [19, 20]. A total of 16 debrief sessions were sufficient to maintain thematic saturation. These debriefs were used to monitor and enhance the trial progress as suggested in other studies [21, 22].

Data collection

The qualitative data were collected during the debrief sessions in the form of focus group discussions. These sessions took place during the recruitment of volunteers and vaccination process, using a semi-structured guide with pre-determined questions that were obtained through reading various related literature [23–26] and the contents refined by the social science team of the trial. The questions pertained to the work done and interaction with both participants and the community team. For example, the interview guide consisted of the following questions: What is the work done by the community team this week? Briefly describe the counseling team’s interaction with the participants. What are the organizational barriers faced, and how were they overcome? What do the volunteers generally think about the trial? And what are the 3 unique/interesting cases this week?. The questions were followed up by several probing questions. The probing questions were designed in such a way that tied to specific initial responses or topics, while also providing interviewers with clear guidelines as described by Robinson [27], to ensure non-directive and contextually relevant application across all interactions. This ensured consistency and transparency in all debrief sessions. A total of 16 debrief sessions were held with the nurse counselors and field workers at different intervals. The two social scientists with extensive qualitative research experience and who were not involved in the HIV vaccine trial conducted these structured debriefs weekly for the first 2 months of the trial and thereafter monthly for the following sessions. Two additional debrief sessions were conducted to gather information on the experiences and updates during the trial. The sessions typically lasted between 20 and 30 min. Session summaries were written on the very same day. The summaries were used to give anonymous feedback during the weekly trial meetings to address logistical issues that would have affected the trial conduct. The anonymized debrief summaries were shared with relevant trial PrEPVacc coordinators using the central database SharePoint.

The role of debriefs in this study

Debrief sessions in this study functioned both as a data collection method and as an embedded component of trial management. As spaces for collective reflection and problem-solving, they enabled nurse counselors to share experiences, refine strategies, and adapt practices over time [28, 29]. This created an inherent feedback loop, whereby the process of data generation might also have influenced the phenomena under study, particularly with respect to evolving recruitment and retention practices. While this dual role introduced potential for socially shaped narratives and the reinforcement of dominant perspectives, it also provided insight into how nurse-counselor practices were actively constructed and modified within trial settings. Debriefs could therefore be understood not only as a methodological tool, but as an integral mechanism through which trial implementation was shaped.

Reflexivity

We made an effort to maintain objectivity throughout the research process by consistently challenging our preconceptions [30, 31]. Throughout the data collection (reflective notes), analysis (bracketing), and outcome interpretation phases (using participant quotes), the authors actively engaged in peer conversations and introspection to identify our biases. We also took into consideration the importance of the interconnected contextual, methodological, interpersonal, and personal elements that could distort the intended meaning from the participants and provided particular strategies for conveying reflexivity in the final findings. Also, since the first four authors who were involved in data collection and analysis were social scientists in the trial, spending some time with participants to build rapport helped to break down the formal hierarchies and encouraged open, honest communication during data collection.

Data analysis

The analysis was initially done in the original language (Kiswahili) after transcription of the audio-recorded data. Then the transcripts were translated into English and back into Kiswahili as per guidelines [32]. This process was essential to ensure integrity and reliability of data and prevent misinterpretation of the concepts. The two authors, MKI and EAMT, independently read both the Kiswahili and English texts to ensure translation consistency; minor corrections were made, including removing personal identifiers.

The content analysis approach proposed by Graneheim and Lundman [33] was used to analyze the data. In this approach, the data were independently coded, leading to similar patterns of codes (categories). The initial categories derived from the codes were progressively clustered based on conceptual similarity. These clusters informed higher-level themes reflecting Embracing the nurse counselors’ responsibilities in the trial, Effective management of volunteers in vaccine trials, and Perceived barriers towards the trial recruitment and retention (Fig. 1).

Fig. 1.

Steps in the analysis process leading to the formation of themes (developed by the authors)

Data analysis followed a systematic, iterative process. The first four authors independently coded the subset of transcripts to obtain a coding framework. The coding process involved an initial reading and re-reading through the text data to identify specific segments of information. This was followed by labeling the segments of information to create codes. Numerous codes were formed at this stage, which were brought into discussion among the independent coders. Codes were compared and refined through discussion, with attention to clarifying definitions and resolving discrepancies. This stage was important to enhance the reliability of the codes [34]. Some codes were agreed upon, while others were deleted or merged. The refined framework was then applied to the full dataset, with ongoing modifications as new patterns emerged. Data coding was managed manually, which was entered into an Excel format for easy processing. The common codes were compared and contrasted to form categories that were as close to the participants’ intended meaning as possible (manifest level of analysis). In this case, categorical statements that best described what transpired from the discussion were constructed to guide the next stage of analysis. To maintain integrity, the first four authors checked the categorical statements against the participants’ original text. Minor differences were discussed and agreed upon. Disagreements were resolved through iterative processes and, where necessary, by revisiting the original data; divergent interpretations were retained. Therefore, all categorical statements that best described the participants’ experience were moved to the next stage of analysis (i.e., latent level of analysis). Reduction of overlapping and redundancy among the categories was performed before engaging in this stage. The latent analysis involves analytical processes that actively use mental schema, theories, and lenses to interpret and understand the data [35]. In this case, we aimed to interpret the meaning embedded in the data to form themes. The use of latent content analysis, therefore, reflected a deliberate analytical choice to move from manifest content to deeper patterns of meaning, rather than a purely descriptive summarization of accounts.

A manifest and latent content analysis approach was applied during the formation of categorical statements and themes, respectively. After analysis, the qualitative data were reported in the form of themes. In the final presentation, the analysis shifted between the categorical statements and the original texts to select sample phrases from the respondents’ voices.

Trustworthiness

To ensure credibility, the interview guide was reviewed by the social science experts to improve the content before data collection. Also, the prolonged period of data collection (up to 26 weeks) helped to engage with study participants. To ensure a rich description of the study methods, we prepared detailed drafts of the study protocol throughout the study. Furthermore, we developed a detailed track record of the data collection process. This activity enhanced the dependability of the study. The use of reflexive journals ensured confirmability.

Ethical approval

The PrEPVacc trial, including all social science studies, was approved by the National Health Research Ethics Committees in Tanzania (Approval number: NIMR/HQ/R.8a/Vol.IX/3333) and the Muhimbili University of Health and Allied Sciences (Approval number: MUHAS-REC-11-2019-066). The social scientists, together with the participants, revisited the study information shared at the previous session to ensure that the participant still recalls what the debrief session was about. Informed consent was obtained from participants, ensuring they understood the study’s objectives, procedures, and risks clearly before participating in the study; this process ensured that participants fully understood their roles in the research. Also, the participants were assured of their freedom to participate or withdraw from the study at any time. They were empowered to make informed decisions about their participation, knowing that their decision, whether to participate or decline, would not impact their employment in the trials. Participants were informed that confidentiality would be protected by removing identifying personal information and guarding against unauthorized access or disclosure of the collected information. During this debriefing session, the participants provided consent to record the conversation.

Findings

Socio-demographic characteristics of participants

Four participants (3 nurse counselors and one field worker) aged between 35 and 48 years old participated in the study. Of the four participants, three were female, and one was a male. All had 3 years of experience in the PrEPVacc trial.

Themes and categories

In the early phase of trial implementation, nurse counselors described considerable uncertainty and emotional strain as they navigated unfamiliar protocols and participant hesitancy. Over time, this initial turbulence gave way to adaptive practices, including more personalized communication and selective prioritization of follow-up efforts. However, while these strategies improved operational efficiency, core challenges related to participant trust and retention persisted across all phases. By the later stages of the trial, recruitment and retention practices appeared more routinized, yet the underlying emotional labor remained, suggesting that such demands are not transient but constitute an enduring feature of frontline trial work. In general, a total of three (3) themes emerged during the discussion. These are (1) Embracing the counselors’ responsibilities in the trial, (2) Effective management of volunteers in vaccine trials, and (3) Perceived barriers in the trial recruitment and retention. These themes were derived from various categories (Table 1).

Table 1.

Themes and categories

No	Category	Theme
1	Enhancing volunteers’ recruitment and enrollment	Embracing the nurse counselors’ responsibilities in the trial
2	Ensuring volunteers’ retention
3	Facilitating trial intervention
1	Availability of a supportive trial environment	Effective management of volunteers in vaccine trials
2	Engagement meeting
3	Collaboration among staff and volunteers
4	Good staff performance and volunteers’ attitude towards the trial
1	Volunteers’ noncompliance with trial requirements	Perceived barriers in the trial recruitment and retention
2	Lack of honesty among PrEPVacc volunteers
3	PrEP-related challenges
4	Personal life and family resistance
5	Stigma and social perception
6	Misconceptions and misinformation about the trial

Theme 1: embracing the counselors’ responsibilities in the trial

This theme emerged from the following categories: enhancing volunteers’ recruitment and enrollment, monitoring the volunteers, ensuring volunteers’ retention, facilitating trial intervention, and providing trial interventions. The subsequent section describes each category in detail.

Enhancing volunteers’ recruitment and enrollment

The nurse counselors described that the screening process to find out if the potential volunteers met the eligibility criteria was one of their essential responsibilities in the trial. They asserted that they were doing different types of activities, such as pre-screening and enrollment of the potential volunteers who met the inclusion criteria. They elaborated that the screening activities were for volunteers enrolled in the trial, and the pre-screening was reserved for the information-giving sessions. In addition, they had to attend to those who were already in the registration cohort as stated below.

We have to attend to the volunteers of the registration cohort, and we do pre-screening to prepare them for enrollment in the vaccine trial. We also teach and provide them with information related to the study vaccinations. (Nurse counselor)

To keep track of the recruitment and enrollment of the volunteers in the trial, the nurse counselors stated that mapping the residential places was one of the important tasks. They stated that they documented the full address and physical location of the volunteers’ residential places so that they could easily access the areas in future follow-up visits. Routinely, they were escorting the volunteers after vaccination so that they could get acquainted with the environment. "The goal was to draw the map of the area as described below by one of the participants:"

What happened is that, if you want to trace this person [volunteer], how to go about it, is documenting it [residential address] down so that if anyone wants to trace it [place], it becomes easy. (Nurse counselor)

Ensuring participants’ retention

The participants expressed devotion to ensuring trial volunteers were retained in the study and followed the prescribed schedule after enrollment. They sent the field workers to track the enrolled volunteers who did not adhere to the scheduled visits. They specifically wanted to know in detail what the problem was. Furthermore, it was revealed that within the activities that took place at the trial site, there were tracking activities that had direct inclusion of the volunteers who joined the trial. In follow-up visits, the participants accounted that the main activity was to review and check participants’ progress, pre-exposure prophylaxis (PrEP) use, contraceptives, and willingness to continue with the study as stated in the following statement:

That follow-up means reviewing the participants by checking their progress, use of prep, contraceptives, and willingness to continue with the study. (Nurse counselor)

Participants also reported that those follow-ups ensured the safety of the volunteers after vaccination. They also added that sometimes the tracking was used by phone, particularly for difficult-to-track volunteers.

Facilitating trial intervention

The participants stated that they were providing an experimental vaccine to the volunteers because they were at risk of being infected with HIV. They elaborated that their main task was to administer the vaccine product and the PrEP materials to the volunteers. They also reported conducting a series of counseling sessions, particularly for volunteers who were enrolled in the trial. Most counseling activities included PrEP adherence, contraception use, and pre-test and post-test counseling. In addition, they verbalized doing urine tests for pregnancy and checking if the volunteers were adhering to PrEP. The urine test for HIV preventive medicine (PrEP) enhanced the provision of counseling to the volunteers, making sure they use it properly.

Theme 2: effective management of volunteers in vaccine trials

In this theme, the availability of support in the trial, such as the engagement meetings, and the supportive trial environment were the main categories discussed in this section.

Availability of a supportive trial environment

The participants reported that they received support from different sources, including the PrEPVacc study volunteers, and this support facilitated their work performance. They stated that taking the volunteers from the study site and escorting them back home was one of the good things that they appreciated. The availability of project vehicles as a means of transport for the volunteers was reported as essential support. They reported that for volunteers who missed visits and could not be accessed by phone, the study tracker visited them physically using the vehicle designated for the trial project. Also, the participants expressed that collaboration and teamwork spirit were important pillars for performing their daily tasks. They appreciated the staff’s effort to work with great cooperation and professionalism. They said that without such collaboration, it would be a stressful work environment that could even make them fail to reach the project’s primary objectives. One of the participants expressed:

…we had a partnership, of course, it [trial conduct] was stressful, but the partnership helped us. If there was no cooperation, some volunteers would have left the clinic at five o’clock [late evening after office hours]. (Nurse counselor)

The participants explained that a high response rate from the potential volunteers in a short time of recruitment was another support that accelerated the progress of the trial. They expressed that the volunteers responded quickly and were readily available for screening and to be recruited in the study. The use of field workers (trackers) was an important aspect that facilitated the attainment of the required number of volunteers in a short time. In addition, the increased trust towards the counselors among volunteers was an essential component that facilitated the work efficiency in the daily activities, as stated below:

Right now there is trust, even if someone [volunteer] has changed the phone number, they look for us that ‘I have changed the phone number’, they update us. (Field worker)

Engagement meetings

The participants in this aspect stated that they used different strategies to manage volunteers during the trial implementation. They said that the use of engagement meetings [volunteers, community advisory board (CAB) members, and trial staff] was a very useful tool that helped to bring the trial volunteers together and to get updates on the trial progress. In these meetings, the volunteers were provided with education while listening to their concerns and giving the needed feedback. They said that the appropriate interventions were undertaken before the concerns piled up to the point of a deterrent from continuing with the trial, as evidenced below:

If something is not right, they say, if they were not treated fairly. They talk about it. I think that is better than if someone just keeps quiet without telling, and we have explained to them that if this person [trial staff] does something wrong to you, you can go and talk to a trusted member of staff, or a CAB member. (Nurse counselor)

Furthermore, the participants expressed that giving freedom of expression to the volunteers was a useful strategy to engage them. This was because most of the volunteers had concerns and were trying as much as possible to express them. In most cases, these concerns appeared to be rumors related to HIV vaccine trials rooted in the community where they came from. Thus, bringing the CAB members to the engagement meetings allowed the volunteers to express their ideas and share experiences with board members, some of whom had participated in the previous vaccine trial. This partnership made the counselors’ task easy, as revealed in the following statement:

Another thing done is to give freedom to the volunteers by bringing them together and being close to the board members [CAB]. If they [volunteers] are free, they can tell you even the challenges that they have to tell the board members. (Nurse counselor)

Collaboration among trial staff and volunteers

The participants identified collaboration among trial staff and volunteers as a key enabler of the trial implementation. This collaboration included effective cooperation between the trial staff and volunteers, clear and direct communication between volunteers and trial staff, and the provision of transportation for the volunteers after receiving the vaccine. They added that the collaboration among the trial staff and the volunteers had greatly improved compared to the beginning of the trial. The following quote further supports this improvement:

The volunteers have shown significant improvement compared to the beginning of the trial; now they properly adhere to their scheduled visits and follow study procedures correctly, which deserves appreciation. Initially, we faced some challenges as has been common when starting new interventions, but the volunteers are now performing exceptionally well. They deserve congratulations for that. (Nurse counselor)

Staff performance and volunteers’ attitudes towards the trial

Participants described good staff performance as pivotal to the success of the trial, significantly contributing to the achievement of daily targets. Two specific attributes that enhanced performance were a strong spirit of teamwork and a hardworking attitude, which enabled the staff to work beyond normal hours despite their limited numbers, as articulated by one of the participants:

I think the main thing is teamwork. Also, it is hard work, although people get tired because of the increased workload. However, still, you find that people [staff] are working hard, and sometimes you find them working beyond working hours. (Nurse counselor)

Participants also reported that the volunteers regarded PrEP pills as any other medication, making it easier for them to use them. The volunteers were reported to demonstrate a positive attitude towards the trial, which enhanced staff performance. This positive attitude was driven by their expectations that the experimental vaccine would be effective and ultimately protect them from contracting HIV due to their risky sexual practices. They argued that the volunteers in the trial had high expectations about the vaccine, and they were excited to be part of the trial, as narrated below:

The way I have seen them, most of them believe that once the vaccine trial is done, it may protect them from HIV due to their behaviour [risky sexual behaviour as sex workers]. (Nurse counselor)

Theme 3: perceived barriers towards the trial recruitment and retention

Participants in this theme were describing the challenges or barriers that impacted recruitment and retention. Although this may be the reflection of the participants’ perspectives, it might be the interpretation and reflection of the trial’s institutional expectation. The following section further provides details.

Challenges adhering to protocol requirements

The participants expressed that, at the beginning of the trial, including the screening phase, adherence to the clinic schedule was a barrier to engaging volunteers in the trial. They explained that many volunteers attended their vaccinations out of their respective schedules (out of window). This imposed a problem on the nurses’/counselors’ daily activities. They reported that some volunteers were less aware of what they were supposed to do at the beginning of the trial, as evidenced below:

It seems that many volunteers did not understand what they came for. We got into the problem of loss to follow up because of that. That bothered us a bit. (Nurse counselor)

Also, the participants reported that some volunteers were not using family planning (FP) methods consistently. They used to take family planning methods from unreliable health facilities or pharmacies. The nurse counselors were skeptical of the authenticity of the FP methods from these health facilities because of a lack of trust, as in the following statement:

Now, at the pharmacy, the owner of the pharmacy is doing business. We do not know what type of FP pills are, how they are stored, what the expiration date is, and if they are being given the same dose or what. (Nurse counselor)

Inconsistent or changing volunteers’ information provided over time

Participants described challenges with volunteers’ adherence to scheduled visits and noted that accounts of behavior sometimes changed over time. These inconsistencies were often interpreted by staff as a lack of honesty. Participants further commented that this perceived lack of honesty among the volunteers was a concern that impacted their engagement in the trial. Initially, participants reported that some of the volunteers were providing unrealistic information, particularly when they wanted them to attend the scheduled visit. This included providing wrong residential addresses, fake phone numbers, and frequently changing mobile phone numbers. Also, they reported that some volunteers were providing incorrect socio-demographic information, including age and occupation. Although mobile phone calls were used as a plausible means of engaging the volunteers in the trial, volunteers frequently changed their mobile phone numbers or provided wrong numbers, thus making them unreachable, as in the following statement:

We have volunteers, with a good relationship with them, although there are also challenges. Some abandon their phone numbers; when you look for them during follow-up, you may find that the number is not reachable. (Nurse counselor)

The participants further explained that when contacted, some volunteers promised to come to the clinic, but only one among several participants contacted came as described below:

Communication is also a challenge, you can call them [volunteers] planning that maybe this day we will screen four, but only one will come. (Nurse counselor)

The participants described that some volunteers demonstrated limited understanding regarding the vaccine trial. They reported that volunteers were worried about receiving the vaccine. This was apparently revealed by some volunteers who dodged while the pharmacist was preparing the drugs for administration. The volunteers ceremoniously left before getting the vaccination dose, as reflected in the statement below:

A volunteer might have consented to be vaccinated …. While waiting to go to the doctor [vaccination provider], you find that she has left, and is not accessible by phone. (Nurse counselor)

The participants reported that some of the volunteers were not honest when inviting them to the engagement meetings. They asserted that these volunteers would decline the invitation, causing unnecessary replacement to fulfill the required number of participants in a particular day. The participant added that the volunteers who declared to decline attending might come in the same day, outnumbering the expected attendance on the given day, as evidenced below:

Sometimes it happens that you may call, informing them not to come, but when you get here, you find they have already come. So again, you have to ask them to leave and come back because they can no longer get services at that time. (Nurse counselor)

PrEP-related challenges

The participants reported that some volunteers experienced side effects such as body malaise, nausea, headaches, excessive hunger, and dizziness. These side effects were often difficult to tolerate and, in some cases, led to volunteers dropping out of the trials, as articulated below:

Another thing that has happened is those side effects of PrEP, especially when a volunteer begins to use them. When somebody gets such a condition, it becomes very difficult to come back … Some may tolerate that temporary condition, but others cannot. …. There are about three volunteers dropped from the trial because of not being able to tolerate those side effects. (Nurse counselor)

Participants also reported that volunteers were concerned about the size of the PrEP pill that they were taking. They added that the Truvada pill was too big and uncomfortable to swallow. They further explained that some volunteers expressed issues about the burden of daily pill-taking and specifically cited the pill size as a challenge, feeling they were unable to swallow it easily compared to other PrEP-related pills. This brought challenges to the nurse counselor as in the following statement:

When it comes to Truvada, many [volunteers] are complaining that the pill is too big, it is scary, and many prefer its size to be like Descovy. (Nurse counselor)

The other concern was about the frequency of taking the PrEP pills, complaining that taking the pill every day was very difficult. The participants reported facing numerous challenges in managing the frequency of PrEP pill-taking, primarily stemming from participant-related factors and logistical barriers within the healthcare system. These concerns were reported to affect volunteers’ trial participation as described by one of the nurse counselors below:

Other volunteers are complaining that they cannot take PrEP every day because of side effects. They say, for instance, that Truvada makes them very hungry. (Nurse counselor)

The other participants reported concern about PrEP containers. They expressed that volunteers were not comfortable with the PrEP container as it resembled an anti-retroviral (ARV) container and was very noisy when shaken. This is because they did not want other people in the community to think of them using ARVs, hence perceived to be HIV positive. They said the volunteers were even afraid of carrying their PrEP when they moved away from home for some days. This barrier was evidenced by the following participant as follows:

Another reason for volunteers’ failure to use PrEP is that the community lacks knowledge about these PrEP pills. Therefore, the community thinks that when a person is seen with those PrEP pills, it means he/she has HIV. (Nurse counselor)

Personal life and family resistance

Participants asserted that personal life and family resistance were also a barrier towards trial recruitment and retention among volunteers. They said that volunteers with a partner or got married the trial participation interfered with their relationship. Although the nurse counselors had counseled them about eligibility and withholding from getting pregnant, this obligation seemed to be less effective in some volunteers making counseling appear ineffective.

That’s the major reason and some have shown that they can no longer continue [with the trial], they have declined, and have withdrawn their consent because they are in a marital relationship and wants to get pregnancy. So, I think those were the major reasons. Additionally, there is one, I think, who said that she was going to get married. (Nurse counselor)

Also, they added that some volunteers had moved out of the study area, thus losing their eligibility for participation. Still, others were occupied with many activities or relocated to other activities, making it difficult for them to continue being part of the trial. One counselor reported how relocation contributed to the barriers in the trial participation:

There are some who have relocated, and they can no longer be there [in the trial]. They have shifted to other regions to seek new life or got new partners outside Dar es Salaam. (Nurse counselor)

Participants expressed that barriers to volunteers’ participation in trials included prohibitions from family members and arguments over HIV testing. Some volunteers were warned by their families about participating in the HIV vaccine trials. Others faced conflicts with their sexual partners due to HIV testing issues, as volunteers would test positive with standard antibody HIV tests. One participant reported a volunteer who encountered resistance from her family:

Another one [volunteer] was prohibited by her family, who said that if they saw her coming here [trial clinic visit] it would be an issue. So she decided to drop out. (Nurse counselor)

Stigma and social perception

The participants expressed that stigma was a significant social barrier that negatively affected the volunteers’ participation in the trial. They said some volunteers were afraid of participation in the trial because of being mistreated and discriminated against, as they were considered to be HIV positive. These negative perceptions were reported to be perpetrated by their sexual partners, close relatives, and people in the surrounding community in which they lived. The major reasons for stigma were the use of the pills (PrEP) that resembled ARVs used by people living with HIV/AIDS. One participant reported:

Stigma must be there …. For example, I met one [volunteer] today saying that she has a sexual partner who has seen them [PrEP pills], okay. Therefore, when it came to having sex, this man did everything to treat her like … like she had been infected with HIV. (Nurse counselor)

For similar reasons, they reported that volunteers were being perceived differently by the community, and this perception negatively affected their participation in the trial. This led to some volunteers being afraid to use PrEP as people in the community would not understand them due to low awareness of PrEP. This scenario was narrated as follows:

I think there is a point given by my colleague that we have a living example of a volunteer who shed her tears that she cannot use those pills because if she moves into her community with them, they would not understand her … (Nurse counselor)

Misconceptions and misinformation

Participants reported misconceptions and misinformation regarding volunteers who were participating in the HIV vaccine trial in the community. Misconception spread in the community through rumors that volunteers were being implanted with HIV. Frequently, some of the volunteers were reported to spread these rumors because of limited knowledge regarding the trial or not being eligible to be enrolled in the trial. These rumors negatively affected other volunteers’ participation in the trial. One counselor reported an experienced misconception in the community that volunteers were being implanted with HIV:

You may find that in a certain location where these volunteers come from, there are rumors like that, that they [volunteers] come here to be implanted with HIV, I don’t know. These [rumors] exist, and I think we have experienced such an issue; there is a participant [volunteer] who decided even to drop from the trial … (Nurse counselor)

Also, the participants reported misinformation regarding the vaccine trial in the community. This misinformation stemmed from volunteers listening to people who did not understand the trial, as well as getting information from other untrusted sources. These sources provided volunteers with incorrect information about the trial, as reported below:

To add on that, the community in which we conduct the trial, often people listen to informal people to get the information. It is much easier for them to listen to a person of their own nature rather than an expert. … We have had that experience even with family planning issues that they listen to their colleagues even if they have never used that method [FP], thinking that the side effects experienced by a colleague will be experienced by everybody. (Nurse counselor)

Discussion

This study explored the experiences of nurse counselors in the recruitment and retention of volunteers in the HIV PrEPVacc trial using a series of structured debriefs. The study revealed that enhancing volunteers’ recruitment and enrollment, ensuring volunteers’ retention, and facilitating trial intervention were the unique experiences that embraced the counselors’ responsibilities in the trial. The availability of a supportive trial environment, engagement meetings, collaboration among staff and volunteers, good staff performance, and volunteers’ attitude towards the trial were the qualities that ensured effective management of volunteers in the trial. However, volunteers’ noncompliance with trial requirements, lack of honesty among volunteers, and PrEP-related challenges were the experience and perceived barriers to trial recruitment and retention. Personal life and family resistance, stigma, and social perception were also encountered as barriers in this study.

Regarding the counselor’s responsibility, enhancing recruitment and retention of participants indicates that nurse counselors are critical to the conduct of clinical trials and are involved in research through diverse roles that are steeped in clinical, ethical, and regulatory challenges [24]. Our findings revealed that ensuring volunteer retention and facilitating trial intervention were the unique functions of nurse counselors for the smooth running of the project. Although retention is the responsibility of the nurse counselors, literature shows that it also involves all other stakeholders in a clinical trial [36, 37]. This underscores the importance of collaboration in clinical trials to enhance the recruitment and retention of study volunteers in future HIV vaccine trials. As has been pointed out elsewhere, good staff performance is vital to ensure the integrity and achievement of key trial goals [38]. It is worth noting that specific clinical trial guidelines, such as adherence to the study protocol and standard operating procedures (SOPs), make a significant contribution to good performance, as described by Sajdak et al. [39]. This is because the study participants integrate specific sections of the guidelines to boost recruitment and retention. The findings in our study revealed that a strong spirit of teamwork and a hardworking attitude enabled the trial team to stretch beyond normal working hours despite the shortage. This is due to the excellent trial working environment that each member of the PrEPVacc team contributed to. Similar findings have been reported in India [37] and the United States of America (USA) [40], whereby a good rapport between the investigating team and the participant plays a vital role in recruitment and retention of study participants.

The availability of a supportive trial environment for effective trial management as described in this study implies that the PrEPVacc trial was conducted according to the standard guidelines, principles, and regulations of clinical trials [41, 42]. These are the mandatory prerequisites for procedures that the study participants experienced during the trial. In addition, the use of vehicles in the study appears to be a useful strategy for tracking the volunteers who missed visits and cannot be accessed by phone. A similar finding has been reported in the USA among the elderly population who were actively tracked [43] as one of the facilitative environments for clinical research to overcome transportation challenges. Engagement meetings in this study were inevitable activities that were used by the study participants to inform the volunteers on the important aspects of the study. Since the clinical trial is a research process that needs volunteers to adhere to the study protocol, engagement meetings are one of the retention strategies [37] and have been used in other HIV vaccine trials among police officers [44, 45] in Tanzania and substance-dependent populations in the USA [46].

The collaboration among the study team for effective management is a complex phenomenon. Our findings imply that handling complexity and conflicts between different expectations and demands in the participants’ and researchers’ contexts requires a collaborative approach for effective management of clinical trials. The handling of such challenges required time, knowledge, interactive learning, and skilled project management as suggested by Alshammari et al. [47]. This study has highlighted some aspects of team functioning that are important for the recruitment and retention of volunteers for clinical trials in Tanzania. While collaboration in our study implied working productively, investing in team members, the study in the USA reported staff shortage and lack of teamwork were barriers for recruitment and retention [48].

The barriers to the recruitment and retention of volunteers to engage in the HIV vaccine trials may be explained by the negative public awareness and inadequate community education about clinical trials [45]. Although the perceived noncompliance with clinical trials and lack of honesty are attributed to specific and intentional behaviors [49], our study shows that many volunteers attended their vaccinations out of their respective schedules, which interfered with the counselors’ daily activities. Such variability in attendance may reflect fluctuating circumstances, concerns about disclosure, or efforts to manage interactions within the trial context. While some barriers were initially described in terms of participant behaviors, a cross-level interpretation suggests that these reflect broader structural constraints, features of trial design, and relational dynamics as reported by Rodríguez-Torres et al. [7]. For example, missed visits were often linked to competing livelihood demands and mobility, compounded by the scheduling demands of the trial protocol. These findings highlight that barriers to participation are not solely located at the individual level but emerge from the interaction of contextual, institutional, and relational factors. This shows that there is a need to embrace specific strategies to enhance the recruitment and retention of volunteers in future trials, as recommended in another study [50]. More focused strategies are needed for retaining the respective volunteers due to the mobile nature of the study population.

The PrEP-related challenge is another concern that contributed to barriers to recruitment and retention in the study. This can be described by the side effects [51–53], size, and appearance of the PrEP pills experienced by the volunteers [54, 55]. This indicates that effective interventions are needed to support PrEP users in accessing, complying with, and retaining volunteers in clinical trials by addressing some PrEP-related changes. Contrary to our study findings, a study in the USA reported that considering alternative PrEP provisions, conducting stigma-reduction campaigns, and increasing capacity for reimbursement for PrEP medications were strategies to increase uptake [56]. Likewise, the strategies can be used to reduce stigma related to PrEP uptake in our study population. The assertion that volunteers’ personal and family factors acted as barriers can be accounted for by the fact that sexual relationships or getting married interfere with trial participation. While this study has shown family or sexual relationships hinder participation in the trial, a study among police officers in the same setting reported strengthened marital relationships after participation in the HIV vaccine trial [44]. This gives the impression that a family or marital relationship is a crucial factor to be considered when recruiting volunteers. The other obstacles, such as relocation of study participants out of the study areas, need to be given special attention when planning mobile populations, such as female sex workers, to participate in HIV vaccine trials. A study review showed that rapport built between the investigating team and the participants plays a vital role in retention [37]. This can also be applied as one of the techniques to enhance recruitment and retention in our study population.

Limitations of the study

Given that data were generated through debrief sessions with trial staff embedded within ongoing trial operations, there is a heightened risk of social desirability and institutional alignment bias. Participants may have been inclined to emphasize successful practices and frame their actions in ways consistent with professional and organizational expectations, potentially underreporting challenges or ethically ambiguous situations. To address this, the analysis actively attended to instances of tension, contradiction, and critical reflection within the data. At the same time, the possibility of underrepresented critical perspectives remains a limitation of the study.

Another limitation is that, although both the nurse counselors and the field worker had the same role: recruiting and retaining the volunteers in the study, the inclusion of a field worker might have diluted the nurse-specific perspectives. However, the information from the field worker did not differ significantly from that of the nurse counselors; hence, it is useful for the current findings.

Implications

This study extends existing literature on trial recruitment and retention by shifting the analytical focus from procedural strategies to the relational and emotional work that underpins their effectiveness. In this study, nurse counselors function as frontline actors who actively mediate between institutional trial requirements and participants’ lived realities. In doing so, they engage in managing uncertainty, distress, and expectations in building and maintaining trust with participants. The findings suggest several operational implications for trial conduct. First, integrating structured, routine debrief sessions (e.g., weekly during active recruitment) can provide a formal mechanism for reflecting on challenges, surfacing ethical tensions, and supporting adaptive practice among frontline staff. Second, targeted training modules focusing on trust-building communication and stigma navigation in retention can strengthen the relational competencies required for sustained participant engagement. Third, proactive community engagement systems, including rumor tracking and rapid response strategies, are essential for maintaining trust and addressing misinformation. Fourthly, incorporating flexible scheduling and feedback-informed adjustments to trial procedures can reduce structural barriers to participation.

Conclusion

The work done by the nurse counselors and community team appears essential in recruiting and retaining volunteers in the HIV vaccine trial. The findings highlight that trial recruitment and retention are not ethically neutral processes but are shaped by ongoing negotiations of power and responsibility. Nurse counselors frequently navigate dual loyalties between meeting institutional expectations for enrollment and retention, and responding to participants’ needs and concerns. Power asymmetries between staff and participants are not only structural but also relational, embedded in dynamics of trust, dependence, and repeated interaction. These findings suggest that ethical trial conduct extends beyond formal consent procedures and requires attention to how power and influence are enacted in everyday recruitment and retention practices. Stigma, misinformation, and social and personal life are the perceived barriers to retention that underscore the collaborative efforts between the volunteers, the study team, and the community for effective participation in the trials.

Authors’ contributions

MKI, EAMT, JSA, and GGL: study conception, planning, design, data analysis, and drafting the manuscript. PM, SA, MB, and EL: study management, coordination, and editing the manuscript. All authors significantly contributed to the manuscript and approved the final version of the manuscript.

Funding

This qualitative study was funded by Gilead. The funder had no role in the design, data collection, analysis, manuscript preparation, or publication of this study.

Data availability

The datasets supporting the conclusions of this article are included within the article and its additional files.

Declarations

Ethics approval and consent to participate

The PrEPVacc trial, including all social science studies, was approved by the National Health Research Ethics Committees in Tanzania (Approval number: NIMR/HQ/R.8a/Vol.IX/3333) and the Muhimbili University of Health and Allied Sciences (Approval number: MUHAS-REC-11-2019-066). The social scientists, together with the participants, revisited the study information shared at the previous session to ensure that the participant still recalls what the debrief session was about. During this debriefing session, the participants were asked for consent to record the conversation. The participants were assured of their freedom to participate or withdraw from the study at any time, and by doing so would not compromise their employment in the trial.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.