Roles of mobile teams in tracing lost to follow–up clients: evidence from the optimization of COVID-19 vaccination uptake and routine immunization in Ekiti State

Abstract

Background

Evidence from literature has established that tracing lost to follow-up clients is an effective strategy for complementing other mechanisms for infectious disease control like human immunodeficiency virus (HIV), tuberculosis, and other diseases such as Ebola. As a long-standing successful public health method of optimizing acceptance and/or adherence to infectious disease treatment tracing lost to follow-up clients is usually carried out by manually investigating individuals who absconded or are absent from treatments designed to manage and/or promote their health status. This study seeks to explore the role of mobile teams in tracing clients lost to follow-up for immunization.

Methods

This study was premised on a qualitative research approach to elicit information from purposively selected populations across 9 local government areas (LGA) in Ekiti state, Nigeria. Focus group discussions, in-depth interviews, and key informant interviews were the selected methods of data collection on the roles of mobile teams in tracing lost to follow–up clients for the optimization of COVID-19 and routine immunization in Ekiti state.

Results

A total of 107 healthcare workers across Ekiti state were selected to participate in this study. Our study found tracing lost to follow-up clients resulted in two major successes for health workers. These are increased awareness of COVID-19 vaccination and routine immunization, and improved vaccination coverage for both categories of vaccinees. Distance between communities, and transportation, were interdependent issues reported by health workers as challenges in the course of their duties.

Conclusion

Our study emphasizes the importance of onboarding and/or training health workers across all categories that are involved in the implementation of a public health program, irrespective of the existing knowledge that they may have on the concept. This study recommends that health workers across all levels, in collaboration with key players and stakeholders employ human-centered designed approaches to improve the sensitization of caregivers, and community populace on the values, benefits, and significance of the COVID-19 vaccination and routine immunization uptake.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-025-12319-2.

Background

The coronavirus 2019 (COVID-19) has infected and led to serious morbidities and mortalities among populations in all countries [1–3]. However, vaccination against the COVID-19 virus emerged as a vital tool to mitigate the consequences of the deadly virus [4, 5]. Three years into the introduction of the COVID-19 vaccine, the administration and acceptance of the vaccines still show significant suboptimal performance [6] due to inequities in vaccine access and the perceived misconception surrounding the vaccine among different populations [7]. Consequently, as of 31st of October 2023, only a little over two-thirds (70.6%) of the world population has received at least one dose of the vaccine with over 13 billion doses being administered globally [8, 9] while about one-quarter (25%) of the population in low and middle-income countries (LMICs) have received at least one dose of the vaccine [10]. Furthermore, the populations in the LMICs are extremely affected by the pandemic as a result of the inequalities that emerged from limited vaccine accessibility, an outcome of incoherent, and unharmonized data to inform targeted interventions to reach underserved populations [7, 11, 12].

The World Health Organization (WHO) announced in May 2020 that about 80 million children younger than 1 year of age were at risk of losing a life-saving vaccination [13], during the peak of the COVID-19 outbreak and erratic prevalence. This suggests that the routine immunization (RI) system was greatly impacted by the COVID-19 pandemic leading to a noticeable decline in vaccination coverage across many countries [3, 14, 15]. This decline led to about 67 million children missing out entirely or partially on routine immunization between 2020 and 2021, leaving them susceptible to various preventable diseases [16]. The COVID-19 pandemic also influenced a rise in misinformation around existing vaccines including measles, pertussis (whooping cough), diphtheria, polio, tuberculosis [17, 18], and in some situations, reduced trust in health services, leading to a reducted hospital visits by people in the LMICs [19, 20]. Therefore, to mitigate the impact of COVID-19 on LMICs, necessary steps were taken to develop a balanced approach that integrates COVID-19 into routine vaccination and the entire primary health care services in several countries [21], as recommended by the WHO.

Evidence from the literature [22–24] have established that tracing lost to follow-up clients is an effective strategy for complementing other mechanisms for infectious diseases control like HIV, tuberculosis, and other diseases such as Ebola. As a long-standing successful public health method of optimizing acceptance and/or adherence to infectious disease treatment [25, 26] tracing lost to follow-up clients is usually carried out by manually investigating individuals who absconded or are absent from treatments designed to manage and/or promote their health status.

Other studies [23, 27, 28] have emphasized that tracing lost to follow-up clients as a strategy for optimizing health services is often difficult and time-consuming. Also, tracing lost to follow-up clients process is usually limited by the number of tracers available, which then limits the process [26] In the context of this study, lost to follow-up clients/defaulters are those who have not completed their COVID-19 vaccination (second dose) and missed their routine immunization antigens (missed children).

As an innovative strategy to optimize COVID-19 vaccination and routine immunization via integration in some selected local government areas (LGAs) in Ekiti state, the Sydani Group through the support of the United States Centre for Disease Control and Prevention (US-CDC), and in collaboration with the Ekiti State Primary Healthcare Development Agency (ESPHCDA) engaged 47 mobile teams to leverage their COVID-19 vaccination exercises to trace under 1 children that are lost to follow-up, for immunization uptake. It is against this backdrop that this study seeks to explore the role of mobile teams in tracing clients lost to follow-up for COVID-19 vaccination and routine immunization.

Methods

This study was premised on a qualitative research approach to elicit information from purposively selected populations across 9 Local Government Areas (LGA) in Ekiti state, Nigeria. Focus group discussions, In-depth interviews, and Key informant interviews were the selected methods of data collection on the roles of mobile teams in tracing clients lost to follow–up for the optimization of COVID-19 and routine immunization in Ekiti state.

Study location

The study was conducted in Ekiti State. A state in southwest Nigeria, Ekiti is bordered by Kwara, Kogi, Ondo, and Osun states. Founded from a portion of Ondo, Kwara and Osun states in 1996 and having Ado-Ekiti as its capital, the state is named after the Ekiti people, a Yoruba subgroup that makes up the bulk of the state's population. Geographically, it is divided between the drier Guinean forest-savanna mosaic and the lowland forests of Nigeria. False acraeas, mona monkeys, forest buffalo, and grey parrot populations are found in the state's natural areas, along with a colony of roughly 20 chimpanzees that is part of one of the last remaining Nigeria-Cameroon chimpanzee populations.

Study participants and selection

Routine immunization is offered in all the primary health care facilities (outside of the health clinics and health posts), and the services are often offered between three days (Tuesdays – Thursdays) depending on the peculiarities of the local government area where the services are being offered. RI services are managed at health facilities by vaccinator(s)/RI focal person (usually the officer-in-charge and second officer-in-charge), a record officer, and in some cases, ward focal person, depending on the locality.

The study participants are health workers at the community level, facility level, local government level (LGA), and caregivers in some of the communities (close to the facilities) where adults and children were traced for vaccination. The health workers are all in the immunization unit of the primary health care agency at the LGA, facility, and community levels. The health workers at the community levels (also known as the mobile team or outreach team) are made up of a 6-member team of health workers (2 vaccinators, 1 mobilizer, 1 validator, 1 Electronic Management of Immunization Data (EMID) recorder, and 1 paper recorder). The vaccinators and EMID recorder among the community health workers are usually members of the primary healthcare facility in the political ward where the facility is situated, while others are ad-hoc and participate in immunization activities. Health workers at the facility level include the Routine Immunization focal Person (RI-FP), and medical recorder officer. Health workers at the LGA level include the Local Government Immunization Officer (LIO) and the Local Health Education Officer (LHEO). A total of 62 interviews (Focus group discussions, in-depth interviews, and key informant interviews) were conducted among health stakeholders and caregivers. Table 1 details the various categories of study participants and the type of interviews conducted with each participant category.

Table 1.

Participants selection in the study locations

Participants	Ekiti State			Total
	FGD	IDI	KII
Community-Level Health Workers
Mobile teams	9			(9*6) 54
Facility Level Health Workers
Routine Immunization Officer		9
Facility Recorder		9
Local government-level actors
Local Government Immunization Officer		9
Local Government Health Education Officer		9
Community Residents
Caregivers			17
Total				107

The study location (Ekiti state) was selected purposively based on the outcome of the COVID-19 vaccination support funded by the US-CDC, and provided to the state, to meet up with the National target of 70% coverage for COVID-19 vaccination as stated by the National Primary Healthcare Development Agency (NPHCDA). Afterwards, the LGA selection was based on the following criteria:

• i.LGAs where mobile teams were deployed.
• ii.Must cut across the three senatorial districts in the state.
• iii.Mobile teams must have visited the facility to acquire documents to trace clients lost to follow-up.

Ekiti state comprises sixteen (16) LGAs. A total of nine (9) LGAs were purposively selected (based on the support provided by Sydani Group) across the three senatorial districts in Ekiti state. A senatorial district represents a territorial division (often marked for geographical and political reasons) wherein a politically elected individual called a senator is elected. The selected LGAs were pre-selected for the integration support to the state to ensure equal representation across the senatorial districts and are. Ado, Emure, Gbonyin, Ido, Ikere, Ijero, Ikole-Ekiti, Irepondun, and Oye Local Government Areas.

Analytical framework

Health systems according to the WHO, consist of organizations, people, and actions whose primary intent is to promote, restore, or maintain health (Global Alliance for Vaccines and Immunization [GAVI], 2013). WHO emphasizes that the health system is a set of interconnected parts that have to function together to be effective, and as a result proposed the six health system building blocks. Managing the interaction of these blocks translates to the achievement of more equitable and sustained improvements across health services and health outcomes.

The WHO Health System Building Framework was adapted in this study to guide the study tool design, data collection, and analysis. Two of the six components of the framework were adapted for the purpose of this study as they are relevant to the operationalization of our objectives (Figure 1).

Fig. 1.

The WHO health systems framework

Ethical approval and consent to participate

This research adhered to the principles outlined in the Helsinki Declaration. Prior to the commencement of the research, informed consent was obtained from each participant. Additionally, the research protocols were approved by the Immunization Research Ethics Committee of the National Emergency Routine Immunization Coordinating Centre (NERICC) of the National Primary Health Care Development Agency (NPHCDA) in Abuja, Nigeria. Having reviewed the protocol, the body waived the need for ethical approval.

Data collection instrument

A semi-structured interview guide was developed using an adapted version of the WHO Health System Building Blocks Framework during the Focus Group Discussions in line with the study objectives [29]. Specifically, our study assessed participants’ understanding and perceptions of tracing lost to follow-up clients, the roles of health workers in tracing clients, and the challenges experienced by the health workers. Additionally, semi-structured guides were also developed for in-depth interviews among health workers at the facility and LGA levels, as well as key informants among the caregivers. These tools were piloted in Ekiti Southwest before being utilized in the selected LGAs.

Data collection procedure

Nine (9) Focus group discussions (FGDs) were conducted among the mobile teams across 9 LGAs in the state. Thirty-six (36) in-depth interviews were conducted among health workers in the facility, and health administrators at the LGA levels across 9 LGAs, while seventeen (17) key informant interviews were conducted among caregivers in at least one community across the 9 selected LGAs. Field notes were taken during the interviews and discussions to corroborate the recordings. Two caregivers (that were traced) were targeted in each LGA, but we could not identify one in one of the LGAs. All interviews and discussions were conducted physically (face-to-face) with the participants. All interviews and discussions were conducted by the research team (a three-man male team), dividing themselves across the 9 LGAs. The research team members are professionals working as research analysts at Sydani Institute for Research and Innovation (SIRI) with a cumulative experience of 13 years, and all hold graduate degrees in the health and social sciences. The research team members are all native Yoruba speakers and also speak English eloquently. Verbal consent was obtained from all the participants before the FGDs/interviews were conducted. All discussions at the LGA and facility levels were conducted in the English language, while discussions at the community level were conducted in the local language (Yoruba) to ease communication within 30–60 min on an audio recording device.

Data analysis

All audio recordings were transcribed in a Word document file by five (5) professional and experienced transcribers. Recordings conducted in local languages were transcribed and back-translated into English language. The research team reviewed the contents of the transcripts and thereafter the codebook was developed.

The transcripts were coded and managed on Dedoose software (version 9.0) by the research team, using both the inductive and deductive approaches. The research team conducted a thematic analysis, and codes were synthesized to identify patterns that could be useful in responding to the study objectives.

Results

This study explored mobile teams' role in tracing lost clients to follow-up. To holistically assess the role of mobile teams, this study considered the knowledge and perceptions of health workers at the facilities and LGA levels, as well as caregivers who were visited during the health workers' mobile programs. Four thematic areas were generated from the study including (i) participants' knowledge and perception of tracing lost to follow-up clients, (ii) roles of mobile teams in tracing lost to follow-up clients, (iii) mobile teams' challenges in tracing lost to follow-up clients, and (iv) factors hindering caregiver’s facility visits for immunizations.

Socio-demographic characteristics of the participants

A total of 107 participants were recruited for the study, they included health workers across the community, facility, and LGA levels, as well as caregivers at the community level. 89.7% of the study participants were females by gender, while only 10.3% of the participants were males. fifty-six 52.3% of participants fall within the 40–49 years age bracket, as 8.4% of the study participants were representatives of the lowest age group in the study (Table 2). The mean age of the study participants was 42.4 ± 8.7 years. 4.7% and 5.6% of the study participants have only primary and secondary education respectively, unlike 60.7% who reported obtaining a higher degree certificate (Table 2).

Table 2.

Socio-demographics characteristics of 107 participants

Characteristics	Frequency (n)	Percent (%)
Gender
Male	11	10.3
Female	96	89.7
Age Group (in years)
20–29	9	8.4
30–39	23	21.5
40–49	56	52.3
50–59 Mean age 42.4	19	17.8
Educational Attainment
Primary	5	4.7
Secondary	6	5.6
Post-Secondary	65	60.7
University	28	26.2
Post-Graduate	3	2.8
	107	100

Participants’ knowledge and perception of tracing lost to follow-up clients

From the discussions held with health workers to assess their understanding of tracing clients lost to follow-up, and how tracing lost to follow-up clients has aided the optimization of COVID-19 vaccination and routine immunization, this theme was further divided into sub-themes to ensure a pragmatic assessment and understanding of health workers responses.

Health workers conception of tracing clients lost to follow-up

In this context, study participants at the community level exuded that their understanding of tracing clients lost to follow-up connotes that it is the process of keeping up with caregivers and children/wards in the various communities within their reach to ensure they complete their vaccination and immunization process to prevent health challenges.

This means locating the people who have not been vaccinated and we can search for them through their cards. We also use our register to identify those who have not received the second or third dose (FGD/Mobile Team/Ijero LGA).

Tracing lost to follow-up means—we’ve taken their information, and we have their contact, when we see that they don’t show up, we take their contact from the register and call them to ask what’s going on. So, during the period of the program, we can call them when we’re going to their areas, and administer their vaccination (FGD/Mobile Team/ LGA level).

To buttress the conception of the community health workers, health workers at the LGA level were also requested to share their understanding of tracing clients lost to follow-up. As such, health workers at the LGA level, also added that tracing clients lost to follow-up is the process of using the available information of caregivers and other community residents to track and locate them for additional vaccine uptake.

Tracing lost to follow up is when the people receiving RI for their children miss doses and we no longer see them. What we do in such cases is that people that have received the first dose already have their information with us so we tell our staff that every Monday, the tickler box or register should be checked to write down the names of the defaulters and in the process, anybody we trace will think they are loved so by that, they will come back to the facility to receive the follow-up dose. Sometimes, we also contact them through the phone (IDI/Health Administrator/LGA level).

In tracing lost to follow-up, trained individuals play a crucial role in ensuring that people who missed their scheduled vaccinations are identified and addressed. They use immunization cards and registers to track who hasn't received their vaccines. The health workers then make calls and conduct mobile in communities to find and bring those individuals in for vaccinations. This process helps ensure that everyone in the community receives the necessary immunizations (IDI/Health Administrator/LGA level).

Requirements of Tracing lost to follow-up clients

Here, participants highlighted that the major requirement for tracing clients lost to follow-up is the vaccination card of the vaccinee, where necessary information of the clients such as the residential address, and the phone number of the clients. This information is then used to trace the clients when necessary and ensure the clients’ uptake of the vaccines.

The requirement for tracing lost to follow-up is the vaccination card. When we realize that someone is supposed to come for vaccination and they do not come, we look for their phone numbers and we call them to remind them of their appointment. Some will come and others may not come and then we locate their households to vaccinate them. On the immunization card, their address and phone numbers are on there. So, when we call and there is no response, we trace the address in the settlement to locate them (FGD/Mobile Team/LGA level).

Let me start from RI, tickler box is usually helpful in this regard especially when we see the defaulters it will help us review their card and we also use defaulters booklet which we use to trace them home and when we ask them why we didn’t see them, some of them say they were ill or has measles or other illnesses as at the time for the RI and this help us to know more the health of such a person, then we do home visit twice a week within the community and we educate them.R5: Also on the COVID, we have a small card of the patient with us which help us to know when they are due for the second dose. (FDG/Mobile Team/LGA level).

Equitable Accessibility to COVID-19 Vaccines and R.I Antigens

Participants expressed that to ensure vaccine accessibility between the categories of vaccinees (the adults for COVID-19 and the children for routine immunization), health workers visiting the various communities go around with two vaccination materials, and also divide the vaccination duties between the two vaccinators that are present in the mobile vaccination team.

Whenever we go for mobile, we ensure that all vaccines are available. Also, when we go the community, since we have two vaccinators, we ask one to handle each vaccine. So, when they bring their card and we see what the child needs, we will vaccinate them accordingly. If the mothers are to receive the COVID-19 vaccine too, I will first attend to the child and then she would receive hers too. (FGD/Mobile Team/LGA level).

We carry two Geosyles, we carry the children’s injections in one, and that of the adults—the COVID-19 vaccine, in the other. That’s how we take them out, and we carry the rest of the resources we need. For COVID-19, we were instructed to do forty per day, and we go with the vaccine for that. For the R.I too, we take them one after the other—Penta 1. If it’s Penta 1, we carry it in bottles. One bottle holds ten, we place it in the Geosyle, and carry it along for the mobile. (FGD/Mobile Team/LGA level).

Roles of mobile teams in tracing lost to follow-up clients

The study assessed the role of mobile teams in both the integration of COVID-19 vaccination and routine immunization, as well as how tracing clients lost to follow-up has helped optimized COVID-19 vaccine/routine immunization uptake. This theme was further divided to include the role of mobile teams, and the support/collaboration health workers received.

Role of Mobile teams in optimizing vaccination and tracing lost to follow-up clients

In describing the roles of mobile teams, participants across the community, facility, and LGA levels emphasized that the mobile team played a significant role in the optimization of COVID-19 vaccination and routine immunization through increased awareness and improved vaccination coverage.

• (i) Increased Awareness

Participants highlighted that community health workers have significantly heightened awareness for COVID-19 vaccination and routine immunization, and in the course of spreading awareness, the health workers found an unusual community (people who move around unclad), wherein the residents are not the usual kind of people health workers come by in their daily routine of mobile awareness for optimized vaccination and immunization knowledge.

They are helping to ensure the information circulate and to make people understand the services better, then about immunization they made people increase in knowledge on it, because they will go to the traditional birth attendants, they will go there and talk to them and they administer the immunization if they find eligible small children they meet there because we always go around with the vaccine and we give them the child welfare card. (IDI/Recorder/ikere LGA).

The mobile team has greatly educated people. Going to these communities have allowed us to reach people we can't even imagine. If we asked them to come, they wouldn't. In fact, I was told that there is a place they went to in this same Emure where people were naked. But they were still able to convince them to get vaccinated as primitive as they were. (IDI/Health worker/LGA level).

• (ii) Improved coverage

Participants believed that the mobile teams’ visitation to several communities established a foundation of vaccine accessibility to diverse categories of individuals in the communities, particularly for individuals who never really showed any form of interest in the COVID-19 vaccination right from inception.

The mobile team is vital in ensuring people who missed previous vaccine sessions are reached. They bring vaccines directly to locations like marketplaces during market days, making it convenient for individuals without disrupting their daily activities. This approach helps overcome challenges like economic constraints and encourages vaccination in different communities. The mobile efforts are supported by stipends and resources from partners like Sydani, including items for awareness campaigns. (IDI/Health Administrator/LGA level).

The mobile team has helped vaccinated people who are far away, busy, financially incapacitated and those who might be nonchalant. So, the mobile team reached them and this helped improve health across board (IDI/Health worker/ LGA level).

Support provided to Community health workers

According to the study participants, the support provided to community health workers came either in the form of collaboration (with the community leaders and the health workers) or financial support provided to health workers to motivate the health workers.

• (i) Collaboration

Participants highlighted that on several occasions they had to collaborate with community leaders to aid their conviction of community residents on the value of COVID-19 vaccination and routine immunization. Participants also added that collaboration with community leaders helped address the issue of language barriers.

Before we start any program, we always invite the traditional leaders and the youth in the communities always have representatives just like the religious leaders and the town chairmen too. The influential people in the community are always useful to keep the work going because we ask them to announce at the meetings in the palace and they disseminate the information to the community members. So, when we get there, it is always easy for us to do our work. (FGD/Mobile Team/ LGA level).

Another thing is that some people among them do not understand the language, so when such a process starts, and they come across someone who is refusing to take it, they beckon on me to reach out to the community leader who understands their language, then the community leader goes there and explain things to them more clearly and debunk rumors. Then direct them to take the vaccine. Some people will never accept such unless they see someone like him who understands their language, (FGD/Mobile Team/LGA level).

Subsequently, participants added that they also collaborated with other health workers at the primary healthcare facility, and outside the primary healthcare system to ensure optimum coverage.

In all the teams in Ekiti, Ado, we all work together. Some people have been referred back to us because the team close to them cannot give the vaccine at the time. They would even joke about how they gave us clients, so there’s harmony between us all(FGD/Mobile Team/LGA level).

We also collaborate with the birth attendants, we have their number and they have ours, whenever they deliver babies, they will call us and we will go there to give immunization because there is an injection, they must take within 24 h of life, we also collaborate with people in the community, the private hospitals. (FDG/Mobile Team/LGA level).

• (ii) Financial Support

On this note, participants highlighted that the financial support offered to them played a significant role in pushing the health workers to desire visiting communities irrespective of the distance, and other potential constraints that may come with such community visitation. Essentially, financial support acted as a form of motivation for community mobile teams.

The support I saw that was given to them was they were paid regularly. Because their mobilizers call me from time to time, saying they saw—I’m talking about the mobile team o, so they tell me that they pay them (IDI/Health Administrator/LGA level).

One of the supports is financial support. The mobile teams were actually mobilized. When we talk of money for transportation, they were mobilized. So that actually gave them the zeal to forge ahead in tracking some of these people. (IDI/Health Administrator/LGA level).

Mobile teams’ challenges in tracing lost to follow-up clients

Health workers at the community, facility, and LGA levels usually work hand in hand to ensure the success of program implementation. As such, all health workers were interviewed to discuss the challenges health workers at the community level experience in the course of tracing defaulters for COVID-19 vaccination and routine immunization. To this end, participants highlighted four key challenges that negatively affect the work of mobile teams.

Distance

Participants complained about the distance between settlements, emphasizing that because the communities are hard-to-reach areas, the health workers have to undergo a lot of stress to ensure they reach those communities and get the people vaccinated to optimize coverage for COVID-19 vaccination and routine Immunization.

Those settlements are far. They are hard-to-reach communities. So sometimes when we want to take bikes, the transport fare is usually exorbitant. Even the roads are not so great, it’s just God’s grace that has been keeping us. (FGD/Mobile Team/LGA level).

The mobile team, the challenges they faced is that the areas they asked them to cover is just too large. It is too much for most of them. The areas to cover were large compared to the number of the teams. There was no problem with the LGA. (IDI/Health Administrator/LGA level)

Transportation

Sequel to the study participants complaints on distance is transportation. Participants reported that transportation is a challenge to their work because of the nature of many of the communities as settlements are dispersed within a particular community and walking down to the various settlements does not exactly fit such situation. Therefore, health workers identify the need to have a mobilization tool in such situations.

The challenges we faced include lack of transportation. Like now, our place here, we have lots of villages—more than fifteen villages that are not on the same route and are far. So, a means of transportation was one of our challenges there. (FGD/Mobile Team/LGA level).

There are also challenges with the transport system because for some settlements the mobile teams are required to trek down from house to house. We also work in the rain sometimes during the rainy season. (IDI/Health Administrator/ LGA level).

Insecurity

Concerns about the safety of community health workers emerged while attempting to understand the issues mobile teams experience on the field. Participants highlighted that their lives feel threatened and used an instance where members of a particular community sternly warned them not to return.

Please sir, if this integration continues, we will need security because it is only God that is saving us. Some of the areas we visit, just immediately we left a young child was reported to be kidnapped. Then, for us working, the situation of things is not good because some of the teams were attacked because they wanted to vaccinate them. (FGD/Mobile Team/LGA level).

Then, for security purposes. Because, in all those local areas, we need security because if you go along with us, you’ll see that lots of places there are scary. We did the NIPDS last, for example, we were going along one community and when they asked where we came from and we told them, they had to warn us not to ever come there anymore. So, that’s part of it. (FGD/Mobile Team/LGA level).

Inaccessibility of defaulters

Interestingly, while this study is all about tracing the clients who missed vaccination or immunization, participants reported the inaccessibility of clients as a challenge. As in many cases, the residential addresses provided on their card are sometimes not correct and the phone numbers might be completely unreachable. Hence, participants shared that:

Hmm, what we encountered at times, you’ll not see those that you even want to see. Some have migrated from here, then some, we’ve not been able to reach them on the phone and we don’t see them. (IDI/Routine Immunization Focal Person/Emure LGA).

Things like that slow down the work because the defaulter you went to his or her house to receive the vaccine and you did not meet at home, this kind of thing can delay one’s work. (IDI/Health Worker/LGA level).

Factors hindering caregiver’s facility visits for immunizations

While tracing clients lost to follow-up is highly useful in identifying caregivers and children who are defaulting in their respective doses of vaccines, the study assessed the conditions that facilitate caregivers’ absence from visiting the health facilities for a subsequent vaccination, or immunization of their children. To this end, participants (health workers and caregivers) reported three key issues resulting in the caregivers’ default. These are lack of transport fare, adverse events following immunization, and caregivers’ complaints of not eating.

Lack of transport fare

On the one hand, health workers reported that in many cases when caregivers were asked why they could not show up at the facility for follow-up immunization, appointments, they were told by the caregivers that the cost of transportation to the facility was an issue for them. On the other hand, responses from the caregivers also corroborate the report from health workers in understanding why caregivers miss immunization appointments.

Some say transport fare is the reason why they cannot come to the center, they say they don’t have money to eat talk less of money to transport to center, but going to meet them in their home has helped to resolve that barrier. And also there are some communities that have bad roads, and the people face a lot of challenges getting to the facility. (FGD/Mobile Team/LGA level).

The reason is that where I live is far and the transport fare is too much, and I don’t have it. (KII/Caregiver/LGA level)

Adverse Events Following Immunization (AEFI)

Participants also reported AEFI as one of the conditions hindering caregivers from visiting the health facilities for subsequent uptake of their children’s immunization. A caregiver further highlighted that her husband instructed her not to visit the facility for follow-up vaccination because of her child’s AEFI experience.

Many of the people we vaccinate, they complain of some side effects of the vaccine, and we inform that the vaccine may meet some illness in their body. This makes these set of people discourage those that have not received the vaccine. This also happens to the children and their caregivers complain too (FGD/Mobile Team/LGA level).

My child reacts to the vaccine he took one time and my husband said that I should take the baby for the vaccine again. – (KII/Caregiver/LGA level)

Caregivers’ complaint of hunger

Furthermore, the participants highlighted that they refused to visit the facility because they were struggling to have something to eat, and they believe that without having adequate food in their stomachs, there was no point coming to get vaccinated.

Hmm, the reason is number one, when a child is not well fed, there’s no way they can take injections. Abi, it’s not possible to take a child—when even I the mother have not eaten, I’ll now say that I want to take my child for immunization when he has not eaten. So, these are the issues. Food is part of it. (KII/Caregiver/LGA level).

Majority of them complain about not having food to eat and money to buy food and that taking vaccine is not a priority for them now (FGD/Mobile Team/LGA level)

Discussion

This study was conducted to explore and understand the roles of mobile teams in optimizing COVID-19 vaccination and routine immunization through tracing of defaulters for both COVID-19 vaccination and routine immunization, thereby filling gaps vis-a-vis the importance of community health workers (mobile teams) in tracing lost to follow-up clients in Ekiti state. Structurally, we categorized findings from our discussion with the study participants into four sections. We commenced by assessing the knowledge and perception of the study participants on the concept of tracing lost to follow-up clients/defaulters. Subsequently, we proceeded to understand the perceptions of our study participants on the role mobile teams play in optimizing vaccination and immunization through tracing of defaulters, in Ekiti state. Thirdly, we assessed the challenges experienced by mobile teams during service delivery to community residents in the state, across all study participants. Finally, we inquired about the conditions hindering caregiver’s facility visits for immunizations.

In exploring participants' knowledge and perception of tracing lost to follow-up clients, our study found that there exists a good knowledge of tracing clients lost to follow-up among health workers at the community and LGA levels, they reported tracing lost to follow-up clients to connote keeping up with defaulters, through available information initially provided to health workers, to ensure their vaccination and/or immunization. This definition is similar to the definition of [30] and [31] in their studies conducted in Ethiopia and Kenya respectively, who defined the concept of Tracing HIV Lost to Follow-Up Clients as clients missing scheduled clinical visits based on previous appointments. This shows that health workers are theoretically, and possibly, pragmatically, abreast of the concepts used in their line of duty, with emphasis on concepts related to tracing lost to follow-up clients. Findings from our study also revealed that a vaccination card is an important tool for tracing defaulters to get them vaccinated, as this contains vital information on locating the vaccinee, as this is based on the reports shared by the study participants. This aligns with the findings of Ateudjieu et al. [32] who reported that the utilization of recorded data to plan catch-up immunization sessions will improve children’s vaccination timeliness, completeness, and coverage.

Through our study findings, participants reported that they go around in different communities with two Geostyle boxes (boxes used in carrying vaccines) to delineate routine immunization antigens from the COVID-19 vaccine and also divide the responsibilities between the two vaccinators that are available in the team, to ensure equitable access to vaccines for children and adults, while also avoiding mix up. This adopted approach may be influenced by the learning acquired from the training offered to health workers before the program implementation. This equally implies that health workers utilize a problem-solving and task-sharing approach in their goal attainment.

Findings from our study revealed that tracing of lost to follow-up clients resulted in two major successes for health workers. These are increased awareness of COVID-19 vaccination and routine immunization for the recipients and their immediate surroundings, and improved vaccination coverage for both categories of vaccines. These achievements may be premised on health workers' visitation of defaulters’ addresses, particularly in remote communities and settlements where caregivers in such settlements may either not be entirely informed about routine immunization or are reluctant to visit health facilities due to the location of childbirth or inadequate financial means to visit health facilities. These achievements are also in line with the assertion and recommendation of Idris et al. [33] who emphasized that the optimization of routine immunization coverage requires a strengthened defaulters tracking system.

Mobile teams’ collaboration with stakeholders at the community level, healthcare providers within and outside the primary healthcare domain (private and public health institutions), and the financial support provided to health workers tremendously influenced the roles played by the mobile teams in the optimization of COVID-19 vaccination and routine immunization. Micek et al. [34] on the success factors for routine immunization performance in Zambia reported that the collaboration of health workers with community leaders to disseminate vaccine messaging to community residents was one of several critical drivers of immunization optimization between 2000 and 2018. Evidence from Nigeria also indicates a successful outcome of the collaborative efforts of health workers and community leaders [35, 36]. Mobile teams’ collaboration with stakeholders and other healthcare providers indicates the effort of the teams’ adherence to the implementation strategy to attain the goal of the implementation of the program, as well as seek redress to all forms of challenges that may be a potential threat to the attainment of the goal.

Findings from our study equally revealed that the distance between communities, as well as transportation, were inter-dependent issues that health workers at the community level vehemently complained about. This corroborates the report of [37]who found limited transportation within rural areas, among other challenges as barriers to mobile clinics' approach to expanded immunization programmes in Northern Cape, South Africa. This complaint, according to the health workers, was a result of the fact that settlements in certain communities within specific LGAs were widely dispersed, and as such became difficult for them to navigate through the settlements in the community. Aside from the distance and transportation, our study also found that insecurity and unavailability of defaulters were other challenges that slowed down the work of community health workers in tracing clients and optimizing COVID-19 vaccination and routine immunization. Fundamentally, security challenges perpetrated by bandits among others, pose a significant threat to health workers who go around several communities to optimize the knowledge of COVID-19 vaccination and routine immunization, as well as optimize both forms of vaccination. Omoleke et al. [38] also identified insecurity as an impediment to the optimal functionality of adverse events following immunization (AEFI) surveillance system in Nigeria.

On the other hand, findings from our study revealed that participants (caregivers) reported lack of transportation fare, adverse events following immunization, and insufficient food intake as barriers to caregivers’ facility visits. The lack of transportation may be influenced by the distance of the nearest health facility to the settlements where such caregivers reside. Subsequently, avoiding health facilities due to AEFI may be based on the caregiver/adult’s limited knowledge of causes of AEFIs, while caregivers’ complaints of insufficient food intake may be premised on the socio-economic status of the caregiver and/or the perception that vaccinees must be well fed to received either COVID-19 vaccination or routine immunization. This corroborates the findings of Kumar et al. [39] and Mahachi et al. [40] who reported financial difficulties, fear of AEFIs, and distance of vaccination centers, among others as the factors hindering children from completing their immunization in Odisha, India, and Nigeria respectively.

Study limitations

One limitation experienced during this study was the unavailability of one caregiver in one of that was traced and immunized in the communities nearer to the primary healthcare facility where the teams were deployed. Additionally, the study did not assess the impediments to contact tracing as a strategy.

Conclusion

Our study emphasizes the importance of onboarding and/or training health workers across all categories involved in public health program implementation, irrespective of their existing knowledge of the concept. This is evident from the fact that the study participants were well-informed and inclined about the concept of tracing follow-up clients/defaulters. In conclusion, our study is an attestation to the fact that the adoption of tracing lost to follow-up clients/defaulters as a complementary strategy in public health interventions, related to providing prophylaxis care and/or panacea, to a specific population or the community at large, is significantly pivotal to the optimization of the services being rendered. This is evident from the recipients' improved awareness of COVID-19 vaccination, routine immunization, and vaccination coverage.

This study recommends that health workers across all levels, in collaboration with key players and stakeholders (including political office holders, traditional leaders, religious leaders, and other influential figures) should employ human-centered designed approaches (taking cues from agile innovation technique) to improve the sensitization of caregivers, and community populace on the values, benefits, and significance of the COVID-19 vaccination and routine immunization uptake. Adopting this approach will help improve the general populace’s access to essential medicines (like vaccines), and health services, and reduce missed vaccinations.

Abbreviations

LMICs

Low and Middle-Income Countries

WHO

World Health Organization

US-CDC

United States Centre for Disease Control and Prevention

ESPHCDA

Ekiti State Primary Healthcare Development Agency

LGA

Local Government Area

EMID

Electronic Management of Immunization Data

RI-FP

Routine Immunization Focal Person

LIO

Local Government Immunization Officer

LHEO

Local (government area) Health Education Officer

NPHCDA

National Primary Healthcare Development Agency

GAVI

Global Alliance for Vaccines and Immunization

COVID-19

Coronavirus 2019

HIV

Human Immunodeficiency Virus

FGD

Focus Group Discussions

IDI

In-depth interviews

KII

Key informant interviews

Authors’ contributions

The article was conceptualized by SDI and MD, and SDI and MD, conducted the qualitative analysis and drafted the manuscript. OWS and SOA reviewed the manuscript and made direct edits on the manuscript. SA and AUJ conducted a programmatic review of the paper to approve any program discussions from the paper. SS oversaw the intervention support provided to the state. DA, SA, OAA, ZA, and CO participated in project implementation in Ekiti state.

Funding

This study did not receive any external funding or grant from any funding agency in the public, commercial, or non-profit sectors.

Data availability

The data supporting the findings will be available from the corresponding author upon request. Requests will be examined and considered on a case-by-case basis.

Declarations

Ethics approval and consent to participate

This research adhered to the principles outlined in the Helsinki Declaration. Prior to the commencement of the research, informed consent was obtained from each participant. Additionally, the research protocols were approved by the Immunization Research Ethics Committee of the National Emergency Routine Immunization Coordinating Centre (NERICC) of the National Primary Health Care Development Agency (NPHCDA) in Abuja, Nigeria. Having reviewed the protocol, the body waived the need for ethical approval.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.