Community engagement for vaccine delivery in low- and middle-income countries and humanitarian settings: A scoping umbrella review

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Polonsky, Rose Burns, Alex Odlum, Yashua Alkali Hamza, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6295865/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Community engagement (CE) is increasingly recognized as a critical strategy for enhancing vaccine delivery in low- and middle-income countries (LMICs) and humanitarian settings, yet the evidence base remains fragmented. This scoping umbrella review synthesizes findings from 24 reviews published between 2013 and 2024, spanning 56 countries, and addressing both routine and outbreak vaccination efforts. CE interventions were found to be consistently associated with improved vaccine acceptance, reduced hesitancy, and increased coverage, particularly in marginalized and hard-to-reach populations. Key mechanisms of success included community participation, two-way communication, local capacity strengthening, and culturally tailored education and outreach efforts. Trusted local actors played a pivotal role in promoting vaccine uptake by addressing misinformation and fostering trust. Interventions involving school- and home-based delivery, mobile technologies, and integrated strategies combining multiple CE components demonstrated the greatest effectiveness. Despite this, substantial definitional ambiguity around CE persists, leading to variation in implementation and evaluation. The review highlights the need for standardized frameworks to define, design, and assess CE in vaccine programs, emphasizing the importance of context-specific adaptation and inclusivity. Moreover, while CE is widely promoted, few studies explored its limitations or cost-effectiveness. In crisis-affected settings, where time and resources are constrained, early, targeted engagement with key community representatives can still foster local ownership and impact. CE must be understood not as an optional add-on, but as a core element of effective, equitable vaccination strategies. Future research should prioritize the development of operational definitions, theories of change, and robust evaluation tools to optimize CE’s impact on immunization outcomes. Health Economics & Outcomes Research Community engagement Vaccination Developing Countries Humanitarian Settings Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Background Vaccination against a range of priority pathogens is a crucial intervention in the arsenal for protecting the public health of populations affected by crises [1]. Indeed, ensuring adequate measles vaccination coverage is recognised as a priority intervention among newly-displaced children by several organisations, including Médecins Sans Frontières (MSF) and the SPHERE project [2,3]. Vaccines can be a cost-effective approach to preventing and mitigating the impacts of infectious disease outbreaks, and reducing overall morbidity and mortality, the overarching aim of humanitarian health interventions. However, humanitarian contexts present particular challenges to vaccine delivery, whether in the maintenance of routine vaccination or the roll-out of vaccination campaigns in response to outbreaks [1]. In particular, these include large-scale populations movements, overburdened and/or dysfunctional health systems, damaged health and transport infrastructure, and security risks to health staff involved in vaccination. These are in addition to other challenges that are universal to vaccination in low- and middle-income countries (LMICs), including logistic considerations (such as the timely importation of sufficient quantity of vaccines and ensuring the cold chain from warehouse to the point of delivery in often remote, hot locations), and ensuring access to vaccination services for the most vulnerable and neglected persons (such as minority groups, young girls, and those residing in hard-to-reach areas). One dimension that is increasingly recognised as a being critical to the success of vaccination efforts is the role of confidence, trust, and acceptance at both the community and individual levels. In recent years, numerous studies have documented the outsized role these play, and of the importance therefore of integrating Risk Communication and Community Engagement (RCCE) into efforts to ensure vaccine uptake. Community Engagement (CE) is broadly understood as efforts to bring together “traditional, community, civil society, government, and opinion groups and leaders; and expanding collective or group roles in addressing the issues that affect their lives” [4]. It refers to the process of working collaboratively with and through groups of people affiliated by geographic proximity, special interest, or similar situations to address issues affecting the well-being of those people. In the context of vaccines, CE entails the active involvement of local communities - through consultation, participation, and partnership - in the planning, implementation, and evaluation of vaccination campaigns. It emphasizes building trust, promoting transparency, addressing cultural sensitivities, and enhancing community ownership of vaccination efforts, aiming to increase vaccine acceptance, address misinformation, and ensure equitable access to immunization services. Despite this increasing recognition of the importance of CE in public health response, efforts to synthesise the evidence concerning the role of CE in vaccine delivery in humanitarian settings have been limited. Much of the existing work has either not addressed the specific application of CE to vaccination, overlooked the nuances of community dynamics, or has focused heavily on economic evaluations without capturing the social and participatory dimensions of CE. Furthermore, the concept of “community” has limitations in certain humanitarian contexts, such as those that involve population displacement and a disruption to traditional community networks and structures [5]. Recent literature has highlighted both the potential and the limitations of CE in vaccination efforts. Evidence has shown that CE can significantly improve vaccine acceptance and coverage rates. The use of behavioural and social approaches to enhance vaccine uptake has been found to effectively address vaccine hesitancy and foster trust in vaccination programs [6,7]. Culturally tailored strategies that incorporate CE have been shown to increase childhood immunization rates by aligning vaccination efforts with local cultural norms and involving community members directly [8]. CE plays a crucial role in vaccination promotion, with high levels of community involvement leading to significant improvements in vaccination rates [9]. These studies collectively underscore that CE is not just a supplementary component but a central strategy in achieving effective vaccination coverage. However, none of these reviews focussed on humanitarian and/or LMIC settings. There is limited understanding on why such CE interventions might be effective, especially in the context of vaccination. Promising mechanisms of change for community engagement interventions in crisis response include the use of existing structures (e.g. known community and opinion leaders); community empowerment (training local people to be involved in the response); and enabling partnership and coordination which avoids duplication of efforts during the crisis [10]. Other reviews of community engagement interventions within the broad context of communicable disease control and health crisis responses did not specifically focus on vaccination efforts, leaving a gap in understanding CE's direct impact on vaccine uptake [10–12]. Insights into the cost-effectiveness of health interventions have also been reported, but the effectiveness of CE interventions for vaccination was not addressed [13]. Finally, some studies focused on the costs associated with promoting vaccination, but these economic evaluations did not explore the broader social dynamics and trust-building that are integral to CE [13,14]. We addressed these evidence synthesis gaps by conducting an umbrella scoping review to describe the landscape of research that has been conducted in the past decade on CE for vaccination in humanitarian and LMIC settings. Methods We followed guidelines on umbrella and scoping reviews while conducting and reporting this research [15–17]. Eligibility criteria Reviews describing CE and vaccine delivery conducted in humanitarian crisis-affected settings and LMICs were eligible for inclusion. We defined crisis-affected settings as those in which ‘an event or series of events has resulted in a critical threat to health, safety, security or well-being of a community or other large group of people’ [18], identifying five conditions, as previously described [19]: (1) progressive loss of livelihoods and deterioration of essential services due to ever-present risk of violence; (2) mass displacement into camp-like settlements; (3) displacement into neighbouring host communities; (4) sudden loss of livelihoods and rapid environmental change due to natural disaster, and (5) food crises. For practical purposes, this amounted to including those countries with humanitarian operation plans during the study period, as published in the OCHA Global Humanitarian Overviews for relevant years [20]. We also included LMICs because much of the evidence and lessons learned from these settings was assumed to apply also to the subset of these countries that have also experienced crises. Furthermore, the term “humanitarian settings” is somewhat intangible and hard-to-define. We used the PICOS framework (population, intervention, comparison, outcome, study design) to develop inclusion and exclusion criteria, which are presented in detail in Table S1: PICOS inclusion and exclusion criteria. Briefly, eligible articles were those in which the study population was people living in humanitarian settings or LMICs, the intervention was some form of CE, the outcome was a measure of vaccination coverage and/or community perception of vaccination activities, with comparison between groups receiving and those not receiving the intervention or between pre- and post-intervention phases. We restricted articles to reviews (both systematic and literature) written in English and published in peer reviewed journals between 2013 and 2024. Search strategy and information sources We restricted our search of relevant articles to PubMed and Google Scholar. On 5 July 2024, we searched PubMed and Google Scholar for entries dated between 2013 and 2024. We specified this ten-year period to ensure that the EVD outbreak in West Africa 2014-2016 was encompassed in its entirety. This global health crisis has been credited in large part with raising awareness about the importance of CE, and ensuring its centrality, in public health emergency response [21]. The full search terms are listed in Supplementary materials 1: Full bibliographic search terms. Studies were imported into Covidence systematic review management software (Veritas Health Innovation) [22]. Entries were checked for duplication. The following steps were then carried out on the deduplicated records independently by two reviewers. Irrelevant articles were excluded in two-steps; first by screening titles and abstracts and then by screening the full text of the remaining articles. Discrepancies and borderline cases were resolved through discussions between at least two reviewers. Data charting process The final list of included articles was divided among reviewers for data charting (extraction and summary) using a structured questionnaire. The data items extracted related to two domains: (1) study metadata: authors, publication year, the years during which the interventions were implemented, the countries of study, and study quality; (2) study detail: vaccine(s) studies, intervention description, intervention impact, and key findings. For charting the intervention description and impact, we mapped the CE activities and outcomes against those listed in an evaluation framework developed by the International Federation of the Red Cross and Red Crescent Societies (IFRC) (Figure S1: Community Engagement Impact Framework). Critical appraisal of individual sources of evidence The quality of the evidence of the included studies was assessed using a methodological quality checklist [23], with each rated “High”, “Medium”, or “Low”. These qualitative scores were taken into consideration at the data synthesis stage to help gauge the quality and strength of the evidence. Synthesis of results We performed a qualitative synthesis of the findings, according to the vaccines of interest, the interventions employed, and the impact of these interventions on different measures of outcome. Findings were grouped according to the interventions and outcomes described in the IFRC evaluation framework. We synthesised and summarised identifiable trends and commonalities in the findings and highlighted important gaps and limitations in the published research. We report our findings according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) statement [24]. Results Selection of sources of evidence The database search initially identified 160 studies. More than half of these (94, 58.8%) were excluded at the abstract screening stage for not meeting the inclusion criteria, leaving 66 for full text screening. Of these, approximately two-thirds (42, 63.6%) were excluded: 16 did not feature a CE intervention, 11 were published prior to 2013, eight were not in LMICs or humanitarian settings, four were not reviews, and three were not concerned with vaccination. This left 24 reviews for inclusion [25–48] (Fig. 1). Characteristics of sources of evidence Characteristics of publications and setting Within the included reviews, studies were conducted in 56 countries across Sub-Saharan Africa, Asia, South and Central America, and Middle East and North Africa (Figure 2). The countries in which the most research was conducted were India and Nigeria (12 reviews each), followed closely by Kenya (11 reviews), Ethiopia (ten reviews), and Pakistan and Zimbabwe (nine reviews each). Two reviews that were based on the same search strategy covered multiple LMICs but did not list the countries [35,47]. Characteristics of research topics Vaccines Research focussed on routine childhood vaccines, with specific mention of tetanus in ten reviews, diphtheria and pertussis in nine, and measles and polio in eight (Figure 3). Human papillomavirus (HPV) vaccination was the focus of five reviews, with bacille Calmette-Guérin (BCG), Hepatitis B, and mumps the focus of two reviews each, and COVID-19, EVD, Haemophilus influenzae type b (Hib), pneumococcal conjugate vaccine (PCV), rotavirus, varicella, and yellow fever featuring in one review each. Twenty reviews were about routine vaccination exclusively, while two were concerned solely with outbreak response vaccination, specifically COVID-19 [43] and EVD [33]. A further two reviews addressed both routine and outbreak response vaccination [37,46]. Interventions Most reviews (N=21, 88%) included “Community participation” as an intervention (Figure 4). “Two-way communication” (n=15, 63%), “Capacity strengthening” (n=14, 58%), and “Community-based activities” (n=12, 50%) were each included in at least half of the reviews. “Research and data” and “Mass communication” were included in ten (42%) and nine (38%) reviews, respectively. The remaining item from the analytical framework, “Coordination and advocacy”, did not feature in any reviews. Outcomes “Efficient response” was the most frequently used measure of outcome, appearing in all (N=24, 100%) reviews, with “Trusted actors and mechanisms” (N=23, 96%) featuring in all-but-one review (Figure 4). “Community cohesion” (N=18, 75%) and “Community-led actions” (N=14, 58%) were included in most reviews, while “Safe and protective behaviours” was included in just seven (29%) reviews. Critical appraisal within sources of evidence The search returned a mix of literature, scoping, and systematic reviews, of varying quality. There were 11 systematic reviews, three scoping reviews, and ten literature reviews. Eleven articles were rated “High” quality, twelve “Medium”, and one “Low”, with the rationale behind each score presented in Annex: Table S4: Quality assessment of included reviews. Two-thirds (n=7, 63.6%) of the systematic reviews were given quality scores of “High”, with the remaining four rated as “Medium" (Figure 5). The three scoping reviews were rated as either “High” or “Medium”. As may be anticipated, the nine literature reviews were generally rated as lower quality compared to the systematic reviews, with just three rated as “High”, six as “Medium”, and the remaining review as “Low”. Synthesis of results Overall, the studies generally suggested that CE interventions play a pivotal role in enhancing vaccination uptake and fostering positive attitudes towards vaccination. The full extraction table is presented in Supplementary Table 3. Using qualitative methods, multiple reviews reported that CE had a notable impact on reducing vaccine hesitancy. Engaging traditional and religious leaders, addressing misinformation, and using tailored communication strategies were particularly effective in overcoming hesitancy in various communities [31,38,39]. CE efforts that involved two-way communication, targeted messaging, and the participation of trusted local figures helped build trust in vaccines, contributing to increased acceptance in settings where hesitancy was initially high [42,46,48]. Most reviews reported that CE interventions led to improved vaccination coverage (as identified through monitoring of localised vaccine uptake). School-based vaccination programs, community volunteer involvement, and community health worker engagement were shown to significantly boost vaccine uptake, especially among hard-to-reach populations [25,29]. Additionally, mobile health technologies like SMS reminders increased coverage by making vaccination efforts more timely and accessible [27]. Tailoring CE efforts to local contexts and involving stakeholders in vaccination processes proved effective in raising immunization rates [30,37,43]. CE also had positive effects on health outcomes by strengthening community resilience and health systems. In settings where CE fostered local ownership and participation, communities were better equipped to sustain vaccination efforts and respond to health challenges [28,35]. This led to improved health system responsiveness and overall better health outcomes, especially in conflict-affected and vulnerable populations [33,34,47]. Community participation and local ownership Community involvement, engagement with leadership, and local ownership were reported to be essential components of successful vaccination programmes, ensuring that initiatives are not imposed by external actors, but co-created, embraced, and championed by the communities themselves. Co-management and co-design approaches, where communities have significant input in planning and executing vaccination initiatives, enhance local ownership and sustainability [32,38,39]. Engagement through local leaders and faith-based outreach significantly improved vaccine uptake in regions with low literacy [47], and forming community health committees empowered local populations to advocate for and sustain vaccination programmes [37]. Lack of community involvement was identified as a crucial constraining factor, while the involvement of key community leaders and representatives was found to be an important facilitating factor [28,31]. Local community participation in service delivery was also reported to aid the successful implementation of vaccination strategies in the DRC through enhanced community access and co-operation [33]. In some settings, education and engagement of traditional and Islamic religious leaders as advocates for vaccination programmes was reported to have helped overcome resistance and improve vaccine uptake [29,31]. Such leaders wield significant influence within their communities and can serve as powerful advocates [48]. This was similarly observed in faith-based outreach efforts in other settings, where engagement with community leaders significantly improved vaccination efforts in low-literacy regions [47]. Conversely, resistance from influential entities, such as the Catholic Church in Kenya, created challenges by disseminating misinformation that undermined confidence in vaccine safety and efficacy [40]. Sustained communication efforts, targeted at key members of the community, including teachers, school boards, community and religious leaders, and parents, were found to be crucial in maintaining community buy-in and support for vaccination [45]. Communication and education Knowledge gaps and misinformation were major contributors to vaccination refusal, and effective communication and education strategies were identified as fundamental to address knowledge gaps, mis- and dis-information, and community concerns regarding vaccination, all of which can jeopardise vaccination efforts [45]. Good knowledge of vaccines and vaccine-preventable diseases among mothers, along with access to mass media, were key predictors of children being fully vaccinated [34,40]. However, while community information sessions in India and Pakistan resulted in greater vaccine knowledge, they did not notably change maternal involvement in decision-making [25]. Therefore, in contexts in which women’s autonomy is limited , engaging fathers and other decision-makers within families may be key to enhancing vaccine uptake [28,34]. Establishing two-way communication channels that permit exchange of information and feedback between health authorities and communities facilitates the real-time identification and addressing of knowledge gaps, misinformation, and concerns [28]. Such channels may be established as part of community-based surveillance systems established for the detection of epidemic-prone diseases and/or post-vaccination monitoring, and which facilitate communication between communities and service providers [28,33,37]. Early community involvement and social mobilization play a pivotal role in laying the groundwork for successful vaccination initiatives. Comprehensive sensitization campaigns co-created with, and disseminated by, trusted sources of information, such as community leaders, teachers, and health workers, was reported to be important for delivering key messages effectively when done prior to the rollout of vaccination campaigns [29,44]. Short, focused messages were reported to be more effective for retaining information and influencing behaviour compared to longer, more generalized sessions. Vaccination completion rates were higher among children of mothers that had received focused education on immunisation of short duration compared with those who had received longer, more general health promotion messages (which also included information on vaccination) [31,40]. This focused messaging was believed to aid retention and recall, whereas the longer sessions led to information overload and a reduced focus on vaccination. In rural Pakistan, brief, health centre-based maternal education during vaccination visits were found to be successful in increasing follow-up rates for subsequent vaccinations [31]. Communication efforts that are tailored to the specific needs and concerns of the target population, and the provision of safe spaces for discussion, enabled adaptive approaches that allowed the concerns of caregivers to be identified and addressed [31]. This may involve making use of various channels such as face-to-face communication, informational materials, and media campaigns to address myths and misconceptions about vaccines while emphasizing their benefits and importance for public health [39,45]. In some settings, multi-stakeholder advocacy strategies have been developed to counter misinformation and disseminate facts about vaccine safety and efficacy, particularly when coordinated with trusted community figures [40]. Addressing misinformation was a key theme that emerged across multiple reviews. Dispelling myths, especially those propagated through social media, was important to improve vaccine confidence [31,32,36]. Communication also had an important role in overcoming public fears and concerns about vaccine safety in the context of COVID-19 [43]. Capacity strengthening and local empowerment Strengthening local capacity, particularly through the training of healthcare workers and community leaders, was identified as having a positive effect on improving vaccination coverage, by helping communities take ownership of vaccination efforts, improving both their quality and reach. Empowering healthcare professionals with the skills necessary to communicate effectively and address vaccine hesitancy was particularly important in low-resource settings [26,37]. Building local capacity ensured the resilience of vaccination programs, particularly in conflict settings, where strong local leadership and system-building were essential for maintaining vaccination efforts [44]. In addition to training healthcare workers, strengthening local leadership and community health systems contributed to long-term sustainability. Empowering local systems helped foster accountability and ensured that vaccination efforts were better integrated into broader public health frameworks [35]. This also ensured that communities could take ownership of vaccination programs, improving both reach and quality [32]. Cultural and social barriers Cultural and social barriers, particularly related to gender roles and decision-making, are significant challenges in achieving broad vaccine coverage. Interventions should be tailored to fit the local context and cultural norms of the communities they serve. This requires a critical appraisal of existing practices and beliefs to ensure that vaccination initiatives are perceived as relevant and beneficial rather than imposing alien practices [31]. For example, it is important to consider the socio-cultural context and power dynamics within communities. In many contexts, including Ethiopia and Kenya, women’s limited autonomy and social standing restrict their ability to make healthcare decisions for themselves and their children, often leading to missed vaccination opportunities [28,34]. Engaging fathers and other male community members in vaccination programs helped address these gender-related barriers, improving vaccine coverage [28,34]. In some contexts, engaging local religious and traditional leaders helped overcome cultural resistance to vaccination. These leaders, when involved in vaccination efforts, significantly increased trust and vaccine acceptance in their communities [31,32]. These studies underscored the importance of addressing social and cultural barriers through community engagement and leadership involvement, particularly in gender-constrained settings [41]. Advocacy, social mobilization, and communication activities using social and mainstream media should contain simple messages that are tailored to varying literacy levels [40]. However, social media can also serve as a barrier, and poor response to vaccination campaigns was reported in areas with higher social media use, which was observed to amplify misinformation [40]. Trust in healthcare providers and systems Several reviews highlighted the importance of localised trust in people they know and engage with directly. For example, trust in local healthcare providers was a crucial factor in vaccine acceptance and adherence. Women in Haiti, for example, were more likely to accept HPV vaccines when recommended by trusted healthcare professionals, such as physicians and community health workers [36]. Similarly, in school-based vaccination programs, schoolteachers, seen as trusted figures, were important in encouraging parents to vaccinate their children [32]. Building trust between healthcare providers and communities was particularly important in settings where misinformation and vaccine hesitancy were prevalent. Trust in health professionals helped counteract fears and concerns about vaccine safety, making healthcare workers key allies in dispelling myths and improving uptake [40]. Community outreach and mobilization Outreach efforts, such as home visits and community mobilization, improved vaccination coverage in hard-to-reach populations. Direct, localized engagement, including home visits and personal communication with caregivers, dispelled myths and educated parents [30,31]. In Ethiopia, the Health Development Army, a community-based initiative, engaged local women’s groups to promote vaccination by fostering a demand-driven approach [34]. Mobilizing communities to participate in vaccination efforts was also a key factor in improving COVID-19 vaccine coverage [43]. Community volunteers play a crucial role in reaching populations resistant to vaccination and facilitating access to vaccination services, although no further detail was provided on the profile and selection process of these volunteers. Their involvement not only expands the reach of vaccination efforts but also fosters trust and acceptance within communities [31]. Targeted and adapted messaging to caregivers, combined with home visits by community health workers (CHWs), was shown to enhance accessibility and engagement among diverse population groups, particularly those that may otherwise be neglected [31]. The establishment of dedicated networks and the holding of regular meetings between the community and health system actors was identified as a potential platform to ensure greater involvement of individuals and communities in generating demand for vaccination services [34]. School and home-based programs have demonstrated success, especially for adolescent-targeted vaccines like HPV. In Rwanda, school-based vaccination programmes were reported to be more effective than facility-based programmes, but it was noted that school attendance is very high in this context [29]. The knowledge and attitude of teachers plays a major role in the success or failure of school-based vaccination programs, and they should therefore be involved in the provision of information to increase confidence in vaccine [40]. This has led to increased acceptability of school-based vaccine among parents and caregivers as teachers played an active role in promoting the vaccine and were seen as trusted stakeholders, and schools as safe havens [40]. However, such programs also required efforts to reach children not enrolled in schools, where a mix of social mobilization and community engagement using community health workers played a critical role in bridging gaps, especially among marginalized communities [29,40]. Home visits also led to higher vaccination uptake due to their ability to facilitate direct personal communication to address concerns and misinformation among mothers [31]. The convenience and efficiency of having vaccines administered at home, and the concomitant involvement of fathers in decision-making, contributed to these gains [31]. Equity and inclusion Equity and inclusion are key features for reaching underserved and marginalized populations during vaccination programmes. Equity-focused interventions helped ensure that vulnerable groups, particularly in rural and hard-to-reach areas, were included in vaccination campaigns [35]. Community feedback mechanisms were important in tailoring programs to local needs and ensuring that vaccination efforts were responsive to the unique challenges faced by different population groups, particularly addressing logistical barriers to access [41]. Involving vulnerable groups from the outset ensured the effectiveness and sustainability of vaccination campaigns [47]. In conflict and post-conflict settings, addressing structural inequalities was key to rebuilding trust in healthcare systems and improving vaccine outcomes [42]. Strengthening local health systems and addressing barriers to access, such as geographic isolation and socioeconomic disadvantage, were successful strategies for ensuring equity in vaccination efforts. Use of mobile and digital technology Mobile health technologies (mHealth), such as SMS reminders, have emerged as promising tools for improving vaccination uptake, particularly in low- and middle-income countries. SMS reminders proved effective in increasing coverage by providing timely information to caregivers, as observed in Zimbabwe, where localized text messages resulted in higher coverage and reduced delays [27,31]. These tools have shown flexibility and can be adapted to different contexts, though their success varies; in high vaccination settings such as Guatemala, SMS reminders had less impact, possibly due to the already high baseline coverage [31]. Despite these variations in success, mHealth technologies offer a flexible, widely available, and low-cost option for improving vaccine adherence in resource-constrained settings [27]. As mobile phone access continues to expand globally, digital interventions are expected to play an increasingly important role in public health, including for vaccination campaigns targeting hard-to-reach populations [43]. Multi-pronged and integrated approaches Multi-component intervention strategies that combine education, outreach, digital tools, and community engagement are among the most effective methods for improving vaccine uptake. These integrated approaches address multiple barriers simultaneously, such as misinformation, logistical challenges, and social resistance, leading to better overall outcomes [31,46]. For instance, combining health education with community mobilization and digital reminders significantly improved vaccination rates in underserved areas. One such intervention package, which included extended service hours and training for healthcare workers, led to substantial improvements in vaccination coverage and reduced dropout rates [31]. Cash transfer incentives, when combined with health education, further incentivized caregivers to vaccinate their children, demonstrating the effectiveness of integrated approaches [46]. For such multi-pronged packages to be used routinely, it would be necessary to identify which combination of interventions produces the greatest impact at the lowest cost, in order to ensure that implementation is sustainable over the long term [31]. Definitional fluidity While CE was consistently emphasized as a critical factor in the success of vaccination programs, its definition and scope often varied considerably, leading to confusion and challenges during implementation. Several reviews pointed out that CE encompassed a wide array of activities, ranging from basic communication efforts to more participatory roles, such as co-management and decision-making with local communities [25,31]. However, without clear frameworks or guidelines, the interpretation of CE became inconsistent, making it difficult to determine what actions truly fell under this umbrella term. The importance of context-specific definitions was also noted, as CE could mean different levels of involvement depending on the setting. In some contexts, activities were limited to one-way information-sharing, while in others, it involved deeper, collaborative efforts that empowered local stakeholders to influence decision-making processes. This fluidity contributed to confusion over what activities should be prioritized and how to best involve communities [38–40]. The variation in the roles of actors, such as teachers or CHWs, further highlighted the need for frameworks that clearly define activities, roles, and the extent of participation to ensure effective CE across diverse contexts. Discussion Summary of evidence We found that community involvement and engagement of leaders are foundational pillars for the success of vaccination programmes. These elements ensure that immunization efforts are not just imposed from external sources but are embraced and championed by the communities themselves. Sustained communication is vital to ensure continued community buy-in and ownership of vaccination efforts. This communication should target key members of the community. By fostering a sense of ownership among these stakeholders, vaccination programs can gain traction and achieve higher levels of acceptance and coverage. Early community involvement and social mobilization play a pivotal role in laying the groundwork for successful vaccination initiatives. Prior to the rollout of vaccination campaigns, comprehensive sensitization campaigns are essential to inform and educate the population about the importance and safety of vaccines. These campaigns often leverage community leaders, teachers, and health workers as trusted sources of information to disseminate key messages effectively. Effective communication and education strategies were found to be indispensable for addressing the various challenges and concerns surrounding vaccination. One crucial aspect is establishing two-way communication channels that allow for the exchange of information and feedback between health authorities and the community. This facilitates the identification and addressing of knowledge gaps, misinformation, and concerns in real-time. Communication strategies should be tailored to the specific needs and concerns of the target population. This may involve utilizing various channels such as face-to-face communication, informational materials, and media campaigns. Moreover, efforts should focus on dispelling myths and addressing misconceptions about vaccines while emphasizing their benefits and importance for public health. Localised trust in people directly known to communities, rather than generic trust in governments, systems, news sources, or institutions, was shown to be important. This critical finding diverges from much current research on trust and is an important factor explaining part of why CE works when it does. In designing vaccination programs, considerations should be given to the socio-cultural context and power dynamics within communities. Interventions should be adapted to fit the local context and cultural norms of the communities they serve. This requires a critical appraisal of existing practices and beliefs to ensure that vaccination initiatives are perceived as relevant and beneficial rather than imposing alien practices. Implementing effective vaccination strategies requires a multifaceted approach that incorporates various tactics and interventions. Leveraging mobile health technologies, such as SMS reminders, can help increase vaccination uptake by providing timely information and reminders to families. Similarly, school- and home-based vaccination programs have demonstrated success, especially when involving teachers and community follow-up to ensure compliance. Community volunteers play a crucial role in reaching populations resistant to vaccination and facilitating access to immunization services. Their involvement not only expands the reach of vaccination efforts but also fosters trust and acceptance within communities. Such multi-pronged approaches to CE create compound effects or changes the intervention context in ways that individual approaches do not always achieve. These findings support the notion that compound approaches to CE create an enabling social and behavioural environment for a broader range and longer duration of CE effects. Education delivery methods should be informed by the preferences and needs of the target audience. Short, focused messages have been shown to be more effective in retaining information and influencing behaviour compared to longer, more generalized sessions. Understanding the factors influencing vaccine acceptance and uptake is essential for developing targeted interventions. The literature identified a range of facilitators, such as confidence in the vaccine, desire to protect loved ones, and trust in healthcare providers. Conversely, barriers to uptake include concerns about potential side effects, vaccine ineffectiveness, and lack of information. Structural barriers, such as limited access to healthcare services and vaccine supplies, also contribute to disparities in vaccination coverage. Addressing these barriers requires comprehensive strategies that consider socio-economic factors, cultural norms, and healthcare infrastructure. While these insights highlight the importance of community involvement and tailored communication strategies, the unique challenges faced in humanitarian contexts must be factored in. In such settings, time is often limited, there is immense pressure to act urgently, and sustained financing remains uncertain. These constraints make it challenging to implement prolonged and comprehensive CE strategies. In such settings, these lessons should be adapted to balance the urgency of response with community needs. For example, this could entail identifying key community representatives early on and focusing on rapid, targeted communication that can still foster a degree of ownership without requiring extensive resources or time. In synthesising these findings, it is important to remember that CE is just one facet of an effective vaccination strategy. Consideration should also be given to such diverse topics as identification of the appropriate target population, ensuring equitable access to vaccine supply and robust supply chain logistics, training and capacity-building of the healthcare workforce, and establishing surveillance to monitor implementation [7,44]. However, it is clear that CE, a topic that has historically not been given adequate consideration, is an essential approach that must be integrated in all vaccination strategies, particular those targeting neglected and under-served populations living in crisis settings. Limitations The major limitations of this review relate to its design as a scoping umbrella review. We limited the search to research that was published between 2013 and 2024, and only those published in English. Furthermore, we searched only two databases, and as this topic is concerned to a large degree with the activities of national and international non-governmental organisations, it is possible that a substantial grey literature (in the form of internal reports and unpublished data) was missed. However, as this was an umbrella review of reviews, these limitations were largely addressed in the methodological approaches of the reviews that formed the basis of our research, which applied less restrictive search strategies. The quality of evidence found was mixed, and generally of a lower quality. This was often connected with study design, such that the literature reviews were generally rated to be of lower quality, which is to be expected. This is not so much a limitation of our methodology, rather a limitation of the quality of the available published literature that formed the basis of our research. This highlights the need for more and higher quality research into the effects of, and best practises for, community engagement in vaccination programs. Finally, an important limitation of this research is that, while all the reviews described examples of what CE could do, none discussed what CE could not do . Further research is needed addressing this gap, which would help address the finding of substantial definitional fluidity regarding what activities do and do not constitute CE. Conclusions As this review highlights, CE is pivotal in addressing myriad challenges, such as distrust in healthcare systems, logistical barriers, and cultural resistance, by actively involving communities in vaccination initiatives. CE fosters trust, ownership, and local leadership, all of which are key to successful vaccination campaigns. Trust is particularly crucial in settings where historical injustices or a lack of transparency have created scepticism towards healthcare interventions. By involving community leaders and stakeholders, CE helps bridge the trust gap and ensures that vaccination efforts are perceived as locally driven rather than imposed by external entities. This sense of ownership, in turn, encourages communities to take an active role in supporting and sustaining vaccination efforts. Additionally, CE initiatives often focus on building local leadership capacities, which helps ensure that the community remains engaged and empowered even after the initial vaccination campaign has ended. This approach not only improves the immediate uptake of vaccines but also contributes to the long-term resilience of healthcare systems in these settings. Strategies that emphasize tailored communication, community participation, and collaboration with influential community leaders can significantly increase vaccine uptake and acceptance. Tailored communication involves adapting messages to align with local cultural norms and values, thereby addressing specific fears or misconceptions that may be prevalent within a community. This approach is particularly effective when combined with the use of trusted figures - such as religious leaders, teachers, or local healthcare workers - who can endorse vaccination and influence public opinion positively. Furthermore, CE initiatives that incorporate educational components help to demystify vaccines, providing communities with accurate information about vaccine safety, efficacy, and the importance of immunization in preventing disease outbreaks. These educational efforts can take various forms, including community meetings, door-to-door outreach, and the use of multimedia tools, all aimed at reaching diverse segments of the population. One of the primary takeaways from this review is the necessity for culturally sensitive, adaptable, and multi-faceted CE interventions. The findings indicate that a one-size-fits-all approach is inadequate, as each setting presents unique socio-cultural dynamics that must be understood and respected for vaccination campaigns to succeed. For instance, in some communities, gender dynamics may play a significant role in healthcare decision-making, necessitating targeted efforts to involve both men and women in CE activities. Successful interventions, such as the involvement of local leaders and use of trusted communication channels, show that culturally embedded strategies help build trust and address vaccine hesitancy more effectively. In settings where misinformation is widespread, engaging community influencers to counteract myths and provide factual information is essential. The involvement of respected community members helps to legitimize vaccination efforts, making them more acceptable to the broader population. Additionally, two-way communication channels were found to be essential, allowing for community feedback and real-time adjustments to vaccination campaigns, thereby enhancing their responsiveness and impact. Such channels ensure that the concerns of community members are heard and addressed, which not only improves trust but also allows health authorities to modify their approaches based on local needs and preferences. This adaptability is particularly important in crisis-affected settings, where conditions can change rapidly, and a flexible approach is needed to maintain the effectiveness of vaccination efforts. Moreover, the integration of mobile health technologies, such as SMS reminders, into CE interventions has proven effective in increasing vaccine coverage by providing timely information and reminders to caregivers, further illustrating the value of a multi-faceted approach. This review demonstrates a need for further research to better define and understand the components of CE in vaccination efforts, as has been previously reported [49]. A consistent theme across the studies was that CE is often vaguely defined and inconsistently applied. Future research should focus on unpacking the concept of CE, defining CE to include clear inclusion and exclusion criteria - what constitutes CE and what does not – to help standardize CE interventions and allow for more rigorous evaluation of their impact. Additionally, creating a comprehensive list of CE interventions and categorizing them based on their effectiveness in different contexts will be vital. This classification can serve as a guide for practitioners, helping them select the most appropriate strategies for specific settings. Another crucial area for future research is measuring the effectiveness (and cost-effectiveness, as resources in humanitarian and low-income settings are often limited) of CE interventions. The development of an evaluation matrix that includes both qualitative and quantitative methods will be necessary to assess the impact of CE activities. This matrix should incorporate indicators such as coverage, timeliness, community attitudes, trust, vaccine hesitancy, and vaccine knowledge. By using tools like network analysis, researchers can better understand the relationships between different CE methods and their outcomes, ultimately identifying the most impactful approaches. An ongoing question in research on CE effectiveness is whether the contextual impact of CE can be measured, given that it is oriented towards creating an enabling environment for vaccine uptake, rather than directly distributing vaccines. Current evaluation approaches may need to explore the impact of CE from a social ecological assessment approach, rather than a traditional monitoring and evaluation approach. This question may be addressed through establishing a theory of change for CE in vaccine delivery, providing a valuable framework for understanding how CE activities contribute to desired outcomes, such as increased vaccine uptake and community resilience. This theory of change would map out the pathways through which CE influences vaccination efforts, from inputs and processes to outputs and outcomes. It would also highlight key assumptions and contextual factors that may affect the success of CE interventions, helping to identify areas where additional support or adaptation may be needed. In conclusion, CE is a powerful tool that can transform vaccine delivery efforts, particularly in vulnerable and underserved populations. By fostering local ownership, improving communication, and involving diverse community actors, CE helps bridge gaps in vaccine access and acceptance. Future vaccination strategies must prioritize and integrate CE as a core element, ensuring that communities are not merely recipients of interventions but active partners whose insights and leadership shape the design, implementation, and sustainability of public health efforts. Moving forward, refining the definition of CE, developing robust evaluation frameworks, and establishing a clear theory of change will be critical to maximizing the impact of CE in vaccination campaigns. References World Health Organization. Vaccination in acute humanitarian emergencies: A framework for decision making. 2017. Available: https://www.who.int/publications/i/item/WHO-IVB-17.03 Médecins Sans Frontières. Refugee Health: An approach to emergency situations. 1997. 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Factors Influencing the Intention and Uptake of COVID-19 Vaccines on the African Continent: A Scoping Review. Vaccines Basel. 2023;11. doi:10.3390/vaccines11040873 O’Rourke J, Yearwood A, Sheaf G, Tomsa S, Bianco V, Mosquera M, et al. What Works to Increase Uptake of Childhood Immunization: A rapid evidence assessment of the impact of interventions targeting caregivers, healthcare workers and communities. UNICEF; 2023. Oketch SY, Ochomo EO, Orwa JA, Mayieka LM, Abdullahi LH. Communication strategies to improve human papillomavirus (HPV) immunisation uptake among adolescents in sub-Saharan Africa: a systematic review and meta-analysis. BMJ Open. 2023;13: e067164. doi:10.1136/bmjopen-2022-067164 Oyo-Ita A, Oduwole O, Arikpo D, Effa EE, Esu EB, Balakrishna Y, et al. Interventions for improving coverage of childhood immunisation in low- and middle-income countries. Cochrane Database Syst Rev. 2023;12: CD008145. doi:10.1002/14651858.CD008145.pub4 Jain M, Duvendack M, Shisler S, Parsekar SS, Leon MDA. Effective interventions for improving routine childhood immunisation in low and middle-income countries: a systematic review of systematic reviews. BMJ Open. 2024;14: e074370. doi:10.1136/bmjopen-2023-074370 Parsekar SS, Vadrevu L, Jain M, Menon S, Taneja G. Interventions addressing routine childhood immunization and its behavioral and social drivers. Front Public Health. 2024;12: 1364798. doi:10.3389/fpubh.2024.1364798 Bain LE, Ngwayu Nkfusai C, Nehwu Kiseh P, Badru OA, Anne Omam L, Adeagbo OA, et al. Community-engagement in research in humanitarian settings. Front Public Health. 2023;11: 1208684. doi:10.3389/fpubh.2023.1208684 Additional Declarations The authors declare no competing interests. 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umbrella review\u003c/p\u003e","fulltext":[{"header":"Background","content":"\u003cp\u003eVaccination against a range of priority pathogens is a crucial intervention in the arsenal for protecting the public health of populations affected by crises [1]. Indeed, ensuring adequate measles vaccination coverage is recognised as a priority intervention among newly-displaced children by several organisations, including M\u0026eacute;decins Sans Fronti\u0026egrave;res (MSF) and the SPHERE project [2,3]. Vaccines can be a cost-effective approach to preventing and mitigating the impacts of infectious disease outbreaks, and reducing overall morbidity and mortality, the overarching aim of humanitarian health interventions.\u003c/p\u003e\n\u003cp\u003eHowever, humanitarian contexts present particular challenges to vaccine delivery, whether in the maintenance of routine vaccination or the roll-out of vaccination campaigns in response to outbreaks [1]. In particular, these include large-scale populations movements, overburdened and/or dysfunctional health systems, damaged health and transport infrastructure, and security risks to health staff involved in vaccination. These are in addition to other challenges that are universal to vaccination in low- and middle-income countries (LMICs), including logistic considerations (such as the timely importation of sufficient quantity of vaccines and ensuring the cold chain from warehouse to the point of delivery in often remote, hot locations), and ensuring access to vaccination services for the most vulnerable and neglected persons (such as minority groups, young girls, and those residing in hard-to-reach areas). One dimension that is increasingly recognised as a being critical to the success of vaccination efforts is the role of confidence, trust, and acceptance at both the community and individual levels. In recent years, numerous studies have documented the outsized role these play, and of the importance therefore of integrating \u003cem\u003eRisk Communication and\u003c/em\u003e \u003cem\u003eCommunity Engagement\u003c/em\u003e (RCCE) into efforts to ensure vaccine uptake.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCommunity Engagement\u003c/em\u003e (CE) is broadly understood as efforts to bring together \u0026ldquo;traditional, community, civil society, government, and opinion groups and leaders; and expanding collective or group roles in addressing the issues that affect their lives\u0026rdquo; [4]. It refers to the process of working collaboratively with and through groups of people affiliated by geographic proximity, special interest, or similar situations to address issues affecting the well-being of those people. In the context of vaccines, CE entails the active involvement of local communities - through consultation, participation, and partnership - in the planning, implementation, and evaluation of vaccination campaigns. It emphasizes building trust, promoting transparency, addressing cultural sensitivities, and enhancing community ownership of vaccination efforts, aiming to increase vaccine acceptance, address misinformation, and ensure equitable access to immunization services.\u003c/p\u003e\n\u003cp\u003eDespite this increasing recognition of the importance of CE in public health response, efforts to synthesise the evidence concerning the role of CE in vaccine delivery in humanitarian settings have been limited. Much of the existing work has either not addressed the specific application of CE to vaccination, overlooked the nuances of community dynamics, or has focused heavily on economic evaluations without capturing the social and participatory dimensions of CE. Furthermore, the concept of \u0026ldquo;community\u0026rdquo; has limitations in certain humanitarian contexts, such as those that involve population displacement and a disruption to traditional community networks and structures [5].\u003c/p\u003e\n\u003cp\u003eRecent literature has highlighted both the potential and the limitations of CE in vaccination efforts. Evidence has shown that CE can significantly improve vaccine acceptance and coverage rates. The use of behavioural and social approaches to enhance vaccine uptake has been found to effectively address vaccine hesitancy and foster trust in vaccination programs [6,7]. Culturally tailored strategies that incorporate CE have been shown to increase childhood immunization rates by aligning vaccination efforts with local cultural norms and involving community members directly [8]. CE plays a crucial role in vaccination promotion, with high levels of community involvement leading to significant improvements in vaccination rates [9]. These studies collectively underscore that CE is not just a supplementary component but a central strategy in achieving effective vaccination coverage. However, none of these reviews focussed on humanitarian and/or LMIC settings. There is limited understanding on why such CE interventions might be effective, especially in the context of vaccination. Promising mechanisms of change for community engagement interventions in crisis response include the use of existing structures (e.g. known community and opinion leaders); community empowerment (training local people to be involved in the response); and enabling partnership and coordination which avoids duplication of efforts during the crisis [10].\u003c/p\u003e\n\u003cp\u003eOther reviews of community engagement interventions within the broad context of communicable disease control and health crisis responses did not specifically focus on vaccination efforts, leaving a gap in understanding CE\u0026apos;s direct impact on vaccine uptake\u0026nbsp;[10\u0026ndash;12]. Insights into the cost-effectiveness of health interventions have also been reported, but the effectiveness of CE interventions for vaccination was not addressed [13]. Finally, some studies focused on the costs associated with promoting vaccination, but these economic evaluations did not explore the broader social dynamics and trust-building that are integral to CE [13,14].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe addressed these evidence synthesis gaps by conducting an umbrella scoping review to describe the landscape of research that has been conducted in the past decade on CE for vaccination in humanitarian and LMIC settings.\u0026nbsp;\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eWe followed guidelines on umbrella and scoping reviews while conducting and reporting this research\u0026nbsp;[15\u0026ndash;17].\u003c/p\u003e\n\u003ch2 id=\"_Toc180576043\"\u003eEligibility criteria\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eReviews describing CE and vaccine delivery conducted in humanitarian crisis-affected settings and LMICs were eligible for inclusion.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe defined crisis-affected settings as those in which \u0026lsquo;an event or series of events has resulted in a critical threat to health, safety, security or well-being of a community or other large group of people\u0026rsquo; [18], identifying five conditions, as previously described [19]: (1) progressive loss of livelihoods and deterioration of essential services due to ever-present risk of violence; (2) mass displacement into camp-like settlements; (3) displacement into neighbouring host communities; (4) sudden loss of livelihoods and rapid environmental change due to natural disaster, and (5) food crises. For practical purposes, this amounted to including those countries with humanitarian operation plans during the study period, as published in the OCHA Global Humanitarian Overviews for relevant years [20].\u003c/p\u003e\n\u003cp\u003eWe also included LMICs because much of the evidence and lessons learned from these settings was assumed to apply also to the subset of these countries that have also experienced crises. Furthermore, the term \u0026ldquo;humanitarian settings\u0026rdquo; is somewhat intangible and hard-to-define.\u003c/p\u003e\n\u003cp\u003eWe used the PICOS framework (population, intervention, comparison, outcome, study design) to develop inclusion and exclusion criteria, which are presented in detail in Table S1: PICOS inclusion and exclusion criteria. Briefly, eligible articles were those in which the study population was people living in humanitarian settings or LMICs, the intervention was some form of CE, the outcome was a measure of vaccination coverage and/or community perception of vaccination activities, with comparison between groups receiving and those not receiving the intervention or between pre- and post-intervention phases. We restricted articles to reviews (both systematic and literature) written in English and published in peer reviewed journals between 2013 and 2024.\u003c/p\u003e\n\u003ch2 id=\"_Toc180576044\"\u003eSearch strategy and\u0026nbsp;information sources\u003c/h2\u003e\n\u003cp\u003eWe restricted our search of relevant articles to PubMed and Google Scholar. On 5 July 2024, we searched PubMed and Google Scholar for entries dated between 2013 and 2024. We specified this ten-year period to ensure that the EVD outbreak in West Africa 2014-2016 was encompassed in its entirety. This global health crisis has been credited in large part with raising awareness about the importance of CE, and ensuring its centrality, in public health emergency response [21]. The full search terms are listed in Supplementary materials 1: Full bibliographic search terms.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eStudies were imported into Covidence systematic review management software (Veritas Health Innovation) [22]. Entries were checked for duplication. The following steps were then carried out on the deduplicated records independently by two reviewers. Irrelevant articles were excluded in two-steps; first by screening titles and abstracts and then by screening the full text of the remaining articles. Discrepancies and borderline cases were resolved through discussions between at least two reviewers.\u003c/p\u003e\n\u003ch2 id=\"_Toc180576045\"\u003eData charting process\u003c/h2\u003e\n\u003cp\u003eThe final list of included articles was divided among reviewers for data charting (extraction and summary) using a structured questionnaire. The data items extracted related to two domains: (1) study metadata: authors, publication year, the years during which the interventions were implemented, the countries of study, and study quality; (2) study detail: vaccine(s) studies, intervention description, intervention impact, and key findings. For charting the intervention description and impact, we mapped the CE activities and outcomes against those listed in an evaluation framework developed by the International Federation of the Red Cross and Red Crescent Societies (IFRC) (Figure S1: Community Engagement Impact Framework).\u003c/p\u003e\n\u003ch2 id=\"_Toc180576046\"\u003eCritical appraisal of\u0026nbsp;individual sources of\u0026nbsp;evidence\u003c/h2\u003e\n\u003cp\u003eThe quality of the evidence of the included studies was assessed using a methodological quality checklist [23], with each rated \u0026ldquo;High\u0026rdquo;, \u0026ldquo;Medium\u0026rdquo;, or \u0026ldquo;Low\u0026rdquo;. These qualitative scores were taken into consideration at the data synthesis stage to help gauge the quality and strength of the evidence.\u003c/p\u003e\n\u003ch2 id=\"_Toc180576047\"\u003eSynthesis of\u0026nbsp;results\u003c/h2\u003e\n\u003cp\u003eWe performed a qualitative synthesis of the findings, according to the vaccines of interest, the interventions employed, and the impact of these interventions on different measures of outcome. Findings were grouped according to the interventions and outcomes described in the IFRC evaluation framework.\u003c/p\u003e\n\u003cp\u003eWe synthesised and summarised identifiable trends and commonalities in the findings and highlighted important gaps and limitations in the published research. We report our findings according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for scoping reviews (PRISMA-ScR) statement [24].\u003c/p\u003e"},{"header":"Results","content":"\u003ch2\u003eSelection of sources of evidence\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eThe database search initially identified 160 studies. More than half of these (94, 58.8%) were excluded at the abstract screening stage for not meeting the inclusion criteria, leaving 66 for full text screening. Of these, approximately two-thirds (42, 63.6%) were excluded: 16 did not feature a CE intervention, 11 were published prior to 2013, eight were not in LMICs or humanitarian settings, four were not reviews, and three were not concerned with vaccination. This left 24 reviews for inclusion [25\u0026ndash;48] (Fig. 1).\u0026nbsp;\u003c/p\u003e\n\u003ch2 id=\"_Toc180576050\"\u003eCharacteristics of sources of evidence\u0026nbsp;\u003c/h2\u003e\n\u003ch3 id=\"_Toc180576051\"\u003eCharacteristics of publications and setting\u0026nbsp;\u003c/h3\u003e\n\u003cp\u003eWithin the included reviews, studies were conducted in 56 countries across Sub-Saharan Africa, Asia, South and Central America, and Middle East and North Africa (Figure 2). The countries in which the most research was conducted were India and Nigeria (12 reviews each), followed closely by Kenya (11 reviews), Ethiopia (ten reviews), and Pakistan and Zimbabwe (nine reviews each). Two reviews that were based on the same search strategy covered multiple LMICs but did not list the countries [35,47].\u0026nbsp;\u003c/p\u003e\n\u003ch3 id=\"_Toc180576052\"\u003eCharacteristics of\u0026nbsp;research topics\u003c/h3\u003e\n\u003ch4\u003eVaccines\u003c/h4\u003e\n\u003cp\u003eResearch focussed on routine childhood vaccines, with specific mention of tetanus in ten reviews, diphtheria and pertussis in nine, and measles and polio in eight (Figure 3). Human papillomavirus (HPV) vaccination was the focus of five reviews, with bacille Calmette-Gu\u0026eacute;rin (BCG), Hepatitis B, and mumps the focus of two reviews each, and COVID-19, EVD, Haemophilus influenzae type b (Hib), pneumococcal conjugate vaccine (PCV), rotavirus, varicella, and yellow fever featuring in one review each.\u003c/p\u003e\n\u003cp\u003eTwenty reviews were about routine vaccination exclusively, while two were concerned solely with outbreak response vaccination, specifically COVID-19 [43] and EVD [33]. A further two reviews addressed both routine and outbreak response vaccination [37,46].\u0026nbsp;\u003c/p\u003e\n\u003ch4\u003eInterventions\u003c/h4\u003e\n\u003cp\u003eMost reviews (N=21, 88%) included \u0026ldquo;Community participation\u0026rdquo; as an intervention (Figure 4). \u0026ldquo;Two-way communication\u0026rdquo; (n=15, 63%), \u0026ldquo;Capacity strengthening\u0026rdquo; (n=14, 58%), and \u0026ldquo;Community-based activities\u0026rdquo; (n=12, 50%) were each included in at least half of the reviews. \u0026ldquo;Research and data\u0026rdquo; and \u0026ldquo;Mass communication\u0026rdquo; were included in ten (42%) and nine (38%) reviews, respectively. The remaining item from the analytical framework, \u0026ldquo;Coordination and advocacy\u0026rdquo;, did not feature in any reviews.\u0026nbsp;\u003c/p\u003e\n\u003ch4\u003eOutcomes\u003c/h4\u003e\n\u003cp\u003e\u0026ldquo;Efficient response\u0026rdquo; was the most frequently used measure of outcome, appearing in all (N=24, 100%) reviews, with \u0026ldquo;Trusted actors and mechanisms\u0026rdquo; (N=23, 96%) featuring in all-but-one review (Figure 4). \u0026ldquo;Community cohesion\u0026rdquo; (N=18, 75%) and \u0026ldquo;Community-led actions\u0026rdquo; (N=14, 58%) were included in most reviews, while \u0026ldquo;Safe and protective behaviours\u0026rdquo; was included in just seven (29%) reviews. \u0026nbsp;\u003c/p\u003e\n\u003ch3 id=\"_Toc180576053\"\u003eCritical appraisal within sources of evidence\u0026nbsp;\u003c/h3\u003e\n\u003cp\u003eThe search returned a mix of literature, scoping, and systematic reviews, of varying quality. There were 11 systematic reviews, three scoping reviews, and ten literature reviews. Eleven articles were rated \u0026ldquo;High\u0026rdquo; quality, twelve \u0026ldquo;Medium\u0026rdquo;, and one \u0026ldquo;Low\u0026rdquo;, with the rationale behind each score presented in Annex: Table S4: Quality assessment of included reviews.\u003c/p\u003e\n\u003cp\u003eTwo-thirds (n=7, 63.6%) of the systematic reviews were given quality scores of \u0026ldquo;High\u0026rdquo;, with the remaining four rated as \u0026ldquo;Medium\u0026quot; (Figure 5). The three scoping reviews were rated as either \u0026ldquo;High\u0026rdquo; or \u0026ldquo;Medium\u0026rdquo;. As may be anticipated, the nine literature reviews were generally rated as lower quality compared to the systematic reviews, with just three rated as \u0026ldquo;High\u0026rdquo;, six as \u0026ldquo;Medium\u0026rdquo;, and the remaining review as \u0026ldquo;Low\u0026rdquo;.\u0026nbsp;\u003c/p\u003e\n\u003ch2 id=\"_Toc180576054\"\u003eSynthesis of results\u0026nbsp;\u003c/h2\u003e\n\u003cp\u003eOverall, the studies generally suggested that CE interventions play a pivotal role in enhancing vaccination uptake and fostering positive attitudes towards vaccination. The full extraction table is presented in Supplementary Table 3.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eUsing qualitative methods, multiple reviews reported that CE had a notable impact on reducing vaccine hesitancy. Engaging traditional and religious leaders, addressing misinformation, and using tailored communication strategies were particularly effective in overcoming hesitancy in various communities [31,38,39]. CE efforts that involved two-way communication, targeted messaging, and the participation of trusted local figures helped build trust in vaccines, contributing to increased acceptance in settings where hesitancy was initially high [42,46,48].\u003c/p\u003e\n\u003cp\u003eMost reviews reported that CE interventions led to improved vaccination coverage (as identified through monitoring of localised vaccine uptake). School-based vaccination programs, community volunteer involvement, and community health worker engagement were shown to significantly boost vaccine uptake, especially among hard-to-reach populations [25,29]. Additionally, mobile health technologies like SMS reminders increased coverage by making vaccination efforts more timely and accessible [27]. Tailoring CE efforts to local contexts and involving stakeholders in vaccination processes proved effective in raising immunization rates [30,37,43].\u003c/p\u003e\n\u003cp\u003eCE also had positive effects on health outcomes by strengthening community resilience and health systems. In settings where CE fostered local ownership and participation, communities were better equipped to sustain vaccination efforts and respond to health challenges [28,35]. This led to improved health system responsiveness and overall better health outcomes, especially in conflict-affected and vulnerable populations [33,34,47].\u0026nbsp;\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576055\"\u003eCommunity participation and local ownership\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eCommunity involvement, engagement with leadership, and local ownership were reported to be essential components of successful vaccination programmes, ensuring that initiatives are not imposed by external actors, but co-created, embraced, and championed by the communities themselves. Co-management and co-design approaches, where communities have significant input in planning and executing vaccination initiatives, enhance local ownership and sustainability [32,38,39]. Engagement through local leaders and faith-based outreach significantly improved vaccine uptake in regions with low literacy [47], and forming community health committees empowered local populations to advocate for and sustain vaccination programmes [37]. Lack of community involvement was identified as a crucial constraining factor, while the involvement of key community leaders and representatives was found to be an important facilitating factor [28,31]. Local community participation in service delivery was also reported to aid the successful implementation of vaccination strategies in the DRC through enhanced community access and co-operation [33].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn some settings, education and engagement of traditional and Islamic religious leaders as advocates for vaccination programmes was reported to have helped overcome resistance and improve vaccine uptake [29,31]. Such leaders wield significant influence within their communities and can serve as powerful advocates [48]. This was similarly observed in faith-based outreach efforts in other settings, where engagement with community leaders significantly improved vaccination efforts in low-literacy regions [47]. Conversely, resistance from influential entities, such as the Catholic Church in Kenya, created challenges by disseminating misinformation that undermined confidence in vaccine safety and efficacy [40].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSustained communication efforts, targeted at key members of the community, including teachers, school boards, community and religious leaders, and parents, were found to be crucial in maintaining community buy-in and support for vaccination [45]. \u0026nbsp;\u003c/p\u003e\n\u003col start=\"2\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576056\"\u003eCommunication and education\u0026nbsp;\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eKnowledge gaps and misinformation were major contributors to vaccination refusal, and effective communication and education strategies were identified as fundamental to address knowledge gaps, mis- and dis-information, and community concerns regarding vaccination, all of which can jeopardise vaccination efforts [45]. Good knowledge of vaccines and vaccine-preventable diseases among mothers, along with access to mass media, were key predictors of children being fully vaccinated [34,40]. However, while community information sessions in India and Pakistan resulted in greater vaccine knowledge, they did not notably change maternal involvement in decision-making [25]. Therefore, in contexts in which women\u0026rsquo;s autonomy is limited\u003cem\u003e,\u0026nbsp;\u003c/em\u003eengaging fathers and other decision-makers within families may be key to enhancing vaccine uptake [28,34].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEstablishing two-way communication channels that permit exchange of information and feedback between health authorities and communities facilitates the real-time identification and addressing of knowledge gaps, misinformation, and concerns [28]. Such channels may be established as part of community-based surveillance systems established for the detection of epidemic-prone diseases and/or post-vaccination monitoring, and which facilitate communication between communities and service providers [28,33,37].\u003c/p\u003e\n\u003cp\u003eEarly community involvement and social mobilization play a pivotal role in laying the groundwork for successful vaccination initiatives. Comprehensive sensitization campaigns co-created with, and disseminated by, trusted sources of information, such as community leaders, teachers, and health workers, was reported to be important for delivering key messages effectively when done prior to the rollout of vaccination campaigns [29,44].\u003c/p\u003e\n\u003cp\u003eShort, focused messages were reported to be more effective for retaining information and influencing behaviour compared to longer, more generalized sessions. Vaccination completion rates were higher among children of mothers that had received focused education on immunisation of short duration compared with those who had received longer, more general health promotion messages (which also included information on vaccination) [31,40]. This focused messaging was believed to aid retention and recall, whereas the longer sessions led to information overload and a reduced focus on vaccination. In rural Pakistan, brief, health centre-based maternal education during vaccination visits were found to be successful in increasing follow-up rates for subsequent vaccinations [31].\u003c/p\u003e\n\u003cp\u003eCommunication efforts that are tailored to the specific needs and concerns of the target population, and the provision of safe spaces for discussion, enabled adaptive approaches that allowed the concerns of caregivers to be identified and addressed [31]. This may involve making use of various channels such as face-to-face communication, informational materials, and media campaigns to address myths and misconceptions about vaccines while emphasizing their benefits and importance for public health [39,45]. In some settings, multi-stakeholder advocacy strategies have been developed to counter misinformation and disseminate facts about vaccine safety and efficacy, particularly when coordinated with trusted community figures [40].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAddressing misinformation was a key theme that emerged across multiple reviews. Dispelling myths, especially those propagated through social media, was important to improve vaccine confidence [31,32,36]. Communication also had an important role in overcoming public fears and concerns about vaccine safety in the context of COVID-19 [43].\u0026nbsp;\u003c/p\u003e\n\u003col start=\"3\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576057\"\u003eCapacity strengthening and local empowerment\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eStrengthening local capacity, particularly through the training of healthcare workers and community leaders, was identified as having a positive effect on improving vaccination coverage, by helping communities take ownership of vaccination efforts, improving both their quality and reach.\u003c/p\u003e\n\u003cp\u003eEmpowering healthcare professionals with the skills necessary to communicate effectively and address vaccine hesitancy was particularly important in low-resource settings [26,37]. Building local capacity ensured the resilience of vaccination programs, particularly in conflict settings, where strong local leadership and system-building were essential for maintaining vaccination efforts [44].\u003c/p\u003e\n\u003cp\u003eIn addition to training healthcare workers, strengthening local leadership and community health systems contributed to long-term sustainability. Empowering local systems helped foster accountability and ensured that vaccination efforts were better integrated into broader public health frameworks [35]. This also ensured that communities could take ownership of vaccination programs, improving both reach and quality [32]. \u0026nbsp;\u003c/p\u003e\n\u003col start=\"4\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576058\"\u003eCultural and social barriers\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eCultural and social barriers, particularly related to gender roles and decision-making, are significant challenges in achieving broad vaccine coverage. Interventions should be tailored to fit the local context and cultural norms of the communities they serve. This requires a critical appraisal of existing practices and beliefs to ensure that vaccination initiatives are perceived as relevant and beneficial rather than imposing alien practices [31]. For example, it is important to consider the socio-cultural context and power dynamics within communities. In many contexts, including Ethiopia and Kenya, women\u0026rsquo;s limited autonomy and social standing restrict their ability to make healthcare decisions for themselves and their children, often leading to missed vaccination opportunities [28,34]. Engaging fathers and other male community members in vaccination programs helped address these gender-related barriers, improving vaccine coverage [28,34].\u003c/p\u003e\n\u003cp\u003eIn some contexts, engaging local religious and traditional leaders helped overcome cultural resistance to vaccination. These leaders, when involved in vaccination efforts, significantly increased trust and vaccine acceptance in their communities [31,32]. These studies underscored the importance of addressing social and cultural barriers through community engagement and leadership involvement, particularly in gender-constrained settings [41].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAdvocacy, social mobilization, and communication activities using social and mainstream media should contain simple messages that are tailored to varying literacy levels [40]. However, social media can also serve as a barrier, and poor response to vaccination campaigns was reported in areas with higher social media use, which was observed to amplify misinformation [40].\u0026nbsp;\u003c/p\u003e\n\u003col start=\"5\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576059\"\u003eTrust in healthcare providers and systems\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eSeveral reviews highlighted the importance of \u003cem\u003elocalised\u003c/em\u003e trust in people they know and engage with directly. For example, trust in local healthcare providers was a crucial factor in vaccine acceptance and adherence. Women in Haiti, for example, were more likely to accept HPV vaccines when recommended by trusted healthcare professionals, such as physicians and community health workers [36]. Similarly, in school-based vaccination programs, schoolteachers, seen as trusted figures, were important in encouraging parents to vaccinate their children [32].\u003c/p\u003e\n\u003cp\u003eBuilding trust between healthcare providers and communities was particularly important in settings where misinformation and vaccine hesitancy were prevalent. Trust in health professionals helped counteract fears and concerns about vaccine safety, making healthcare workers key allies in dispelling myths and improving uptake [40].\u0026nbsp;\u003c/p\u003e\n\u003col start=\"6\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576060\"\u003eCommunity outreach and mobilization\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eOutreach efforts, such as home visits and community mobilization, improved vaccination coverage in hard-to-reach populations. Direct, localized engagement, including home visits and personal communication with caregivers, dispelled myths and educated parents [30,31]. In Ethiopia, the Health Development Army, a community-based initiative, engaged local women\u0026rsquo;s groups to promote vaccination by fostering a demand-driven approach [34]. Mobilizing communities to participate in vaccination efforts was also a key factor in improving COVID-19 vaccine coverage [43].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCommunity volunteers play a crucial role in reaching populations resistant to vaccination and facilitating access to vaccination services, although no further detail was provided on the profile and selection process of these volunteers. Their involvement not only expands the reach of vaccination efforts but also fosters trust and acceptance within communities [31]. Targeted and adapted messaging to caregivers, combined with home visits by community health workers (CHWs), was shown to enhance accessibility and engagement among diverse population groups, particularly those that may otherwise be neglected [31]. The establishment of dedicated networks and the holding of regular meetings between the community and health system actors was identified as a potential platform to ensure greater involvement of individuals and communities in generating demand for vaccination services [34].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSchool and home-based programs have demonstrated success, especially for adolescent-targeted vaccines like HPV. In Rwanda, school-based vaccination programmes were reported to be more effective than facility-based programmes, but it was noted that school attendance is very high in this context [29]. The knowledge and attitude of teachers plays a major role in the success or failure of school-based vaccination programs, and they should therefore be involved in the provision of information to increase confidence in vaccine [40]. This has led to increased acceptability of school-based vaccine among parents and caregivers as teachers played an active role in promoting the vaccine and were seen as trusted stakeholders, and schools as safe havens [40].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHowever, such programs also required efforts to reach children not enrolled in schools, where a mix of social mobilization and community engagement using community health workers played a critical role in bridging gaps, especially among marginalized communities [29,40].\u003c/p\u003e\n\u003cp\u003eHome visits also led to higher vaccination uptake due to their ability to facilitate direct personal communication to address concerns and misinformation among mothers [31]. The convenience and efficiency of having vaccines administered at home, and the concomitant involvement of fathers in decision-making, contributed to these gains [31].\u0026nbsp;\u003c/p\u003e\n\u003col start=\"7\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576061\"\u003eEquity and inclusion\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eEquity and inclusion are key features for reaching underserved and marginalized populations during vaccination programmes. Equity-focused interventions helped ensure that vulnerable groups, particularly in rural and hard-to-reach areas, were included in vaccination campaigns [35]. Community feedback mechanisms were important in tailoring programs to local needs and ensuring that vaccination efforts were responsive to the unique challenges faced by different population groups, particularly addressing logistical barriers to access [41]. Involving vulnerable groups from the outset ensured the effectiveness and sustainability of vaccination campaigns [47].\u003c/p\u003e\n\u003cp\u003eIn conflict and post-conflict settings, addressing structural inequalities was key to rebuilding trust in healthcare systems and improving vaccine outcomes [42]. Strengthening local health systems and addressing barriers to access, such as geographic isolation and socioeconomic disadvantage, were successful strategies for ensuring equity in vaccination efforts.\u0026nbsp;\u003c/p\u003e\n\u003col start=\"8\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576062\"\u003eUse of mobile and digital technology\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eMobile health technologies (mHealth), such as SMS reminders, have emerged as promising tools for improving vaccination uptake, particularly in low- and middle-income countries. SMS reminders proved effective in increasing coverage by providing timely information to caregivers, as observed in Zimbabwe, where localized text messages resulted in higher coverage and reduced delays [27,31]. These tools have shown flexibility and can be adapted to different contexts, though their success varies; in high vaccination settings such as Guatemala, SMS reminders had less impact, possibly due to the already high baseline coverage [31].\u003c/p\u003e\n\u003cp\u003eDespite these variations in success, mHealth technologies offer a flexible, widely available, and low-cost option for improving vaccine adherence in resource-constrained settings [27]. As mobile phone access continues to expand globally, digital interventions are expected to play an increasingly important role in public health, including for vaccination campaigns targeting hard-to-reach populations [43].\u0026nbsp;\u003c/p\u003e\n\u003col start=\"9\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576063\"\u003eMulti-pronged and integrated approaches\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eMulti-component intervention strategies that combine education, outreach, digital tools, and community engagement are among the most effective methods for improving vaccine uptake. These integrated approaches address multiple barriers simultaneously, such as misinformation, logistical challenges, and social resistance, leading to better overall outcomes [31,46].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor instance, combining health education with community mobilization and digital reminders significantly improved vaccination rates in underserved areas. One such intervention package, which included extended service hours and training for healthcare workers, led to substantial improvements in vaccination coverage and reduced dropout rates [31]. Cash transfer incentives, when combined with health education, further incentivized caregivers to vaccinate their children, demonstrating the effectiveness of integrated approaches [46].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eFor such multi-pronged packages to be used routinely, it would be necessary to identify which combination of interventions produces the greatest impact at the lowest cost, in order to ensure that implementation is sustainable over the long term [31].\u0026nbsp;\u003c/p\u003e\n\u003col start=\"10\"\u003e\n \u003cli\u003e\n \u003ch3 id=\"_Toc180576064\"\u003eDefinitional fluidity\u003c/h3\u003e\n \u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003eWhile CE was consistently emphasized as a critical factor in the success of vaccination programs, its definition and scope often varied considerably, leading to confusion and challenges during implementation. Several reviews pointed out that CE encompassed a wide array of activities, ranging from basic communication efforts to more participatory roles, such as co-management and decision-making with local communities [25,31]. However, without clear frameworks or guidelines, the interpretation of CE became inconsistent, making it difficult to determine what actions truly fell under this umbrella term.\u003c/p\u003e\n\u003cp\u003eThe importance of context-specific definitions was also noted, as CE could mean different levels of involvement depending on the setting. In some contexts, activities were limited to one-way information-sharing, while in others, it involved deeper, collaborative efforts that empowered local stakeholders to influence decision-making processes. This fluidity contributed to confusion over what activities should be prioritized and how to best involve communities [38\u0026ndash;40]. The variation in the roles of actors, such as teachers or CHWs, further highlighted the need for frameworks that clearly define activities, roles, and the extent of participation to ensure effective CE across diverse contexts.\u0026nbsp;\u003c/p\u003e"},{"header":"Discussion","content":"\u003ch2\u003eSummary of\u0026nbsp;evidence\u003c/h2\u003e\n\u003cp\u003eWe found that community involvement and engagement of leaders are foundational pillars for the success of vaccination programmes. These elements ensure that immunization efforts are not just imposed from external sources but are embraced and championed by the communities themselves. Sustained communication is vital to ensure continued community buy-in and ownership of vaccination efforts. This communication should target key members of the community. By fostering a sense of ownership among these stakeholders, vaccination programs can gain traction and achieve higher levels of acceptance and coverage.\u003c/p\u003e\n\u003cp\u003eEarly community involvement and social mobilization play a pivotal role in laying the groundwork for successful vaccination initiatives. Prior to the rollout of vaccination campaigns, comprehensive sensitization campaigns are essential to inform and educate the population about the importance and safety of vaccines. These campaigns often leverage community leaders, teachers, and health workers as trusted sources of information to disseminate key messages effectively.\u003c/p\u003e\n\u003cp\u003eEffective communication and education strategies were found to be indispensable for addressing the various challenges and concerns surrounding vaccination. One crucial aspect is establishing two-way communication channels that allow for the exchange of information and feedback between health authorities and the community. This facilitates the identification and addressing of knowledge gaps, misinformation, and concerns in real-time.\u003c/p\u003e\n\u003cp\u003eCommunication strategies should be tailored to the specific needs and concerns of the target population. This may involve utilizing various channels such as face-to-face communication, informational materials, and media campaigns. Moreover, efforts should focus on dispelling myths and addressing misconceptions about vaccines while emphasizing their benefits and importance for public health.\u003c/p\u003e\n\u003cp\u003eLocalised trust in people directly known to communities, rather than generic trust in governments, systems, news sources, or institutions, was shown to be important. This critical finding diverges from much current research on trust and is an important factor explaining part of \u003cem\u003ewhy\u003c/em\u003e CE works when it does.\u003c/p\u003e\n\u003cp\u003eIn designing vaccination programs, considerations should be given to the socio-cultural context and power dynamics within communities. Interventions should be adapted to fit the local context and cultural norms of the communities they serve. This requires a critical appraisal of existing practices and beliefs to ensure that vaccination initiatives are perceived as relevant and beneficial rather than imposing alien practices.\u003c/p\u003e\n\u003cp\u003eImplementing effective vaccination strategies requires a multifaceted approach that incorporates various tactics and interventions. Leveraging mobile health technologies, such as SMS reminders, can help increase vaccination uptake by providing timely information and reminders to families. Similarly, school- and home-based vaccination programs have demonstrated success, especially when involving teachers and community follow-up to ensure compliance. Community volunteers play a crucial role in reaching populations resistant to vaccination and facilitating access to immunization services. Their involvement not only expands the reach of vaccination efforts but also fosters trust and acceptance within communities. Such multi-pronged approaches to CE create compound effects or changes the intervention context in ways that individual approaches do not always achieve. These findings support the notion that compound approaches to CE create an enabling social and behavioural environment for a broader range and longer duration of CE effects.\u003c/p\u003e\n\u003cp\u003eEducation delivery methods should be informed by the preferences and needs of the target audience. Short, focused messages have been shown to be more effective in retaining information and influencing behaviour compared to longer, more generalized sessions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eUnderstanding the factors influencing vaccine acceptance and uptake is essential for developing targeted interventions. The literature identified a range of facilitators, such as confidence in the vaccine, desire to protect loved ones, and trust in healthcare providers. Conversely, barriers to uptake include concerns about potential side effects, vaccine ineffectiveness, and lack of information. Structural barriers, such as limited access to healthcare services and vaccine supplies, also contribute to disparities in vaccination coverage. Addressing these barriers requires comprehensive strategies that consider socio-economic factors, cultural norms, and healthcare infrastructure.\u003c/p\u003e\n\u003cp\u003eWhile these insights highlight the importance of community involvement and tailored communication strategies, the unique challenges faced in humanitarian contexts must be factored in. In such settings, time is often limited, there is immense pressure to act urgently, and sustained financing remains uncertain. These constraints make it challenging to implement prolonged and comprehensive CE strategies. In such settings, these lessons should be adapted to balance the urgency of response with community needs. For example, this could entail identifying key community representatives early on and focusing on rapid, targeted communication that can still foster a degree of ownership without requiring extensive resources or time.\u003c/p\u003e\n\u003cp\u003eIn synthesising these findings, it is important to remember that CE is just one facet of an effective vaccination strategy. Consideration should also be given to such diverse topics as identification of the appropriate target population, ensuring equitable access to vaccine supply and robust supply chain logistics, training and capacity-building of the healthcare workforce, and establishing surveillance to monitor implementation [7,44]. However, it is clear that CE, a topic that has historically not been given adequate consideration, is an essential approach that must be integrated in all vaccination strategies, particular those targeting neglected and under-served populations living in crisis settings.\u0026nbsp;\u003c/p\u003e\n\u003ch2 id=\"_Toc180576067\"\u003eLimitations\u003c/h2\u003e\n\u003cp\u003eThe major limitations of this review relate to its design as a scoping umbrella review. We limited the search to research that was published between 2013 and 2024, and only those published in English. Furthermore, we searched only two databases, and as this topic is concerned to a large degree with the activities of national and international non-governmental organisations, it is possible that a substantial grey literature (in the form of internal reports and unpublished data) was missed. However, as this was an umbrella review of reviews, these limitations were largely addressed in the methodological approaches of the reviews that formed the basis of our research, which applied less restrictive search strategies.\u003c/p\u003e\n\u003cp\u003eThe quality of evidence found was mixed, and generally of a lower quality. This was often connected with study design, such that the literature reviews were generally rated to be of lower quality, which is to be expected. This is not so much a limitation of our methodology, rather a limitation of the quality of the available published literature that formed the basis of our research. This highlights the need for more and higher quality research into the effects of, and best practises for, community engagement in vaccination programs.\u003c/p\u003e\n\u003cp\u003eFinally, an important limitation of this research is that, while all the reviews described examples of what CE could do, none discussed what CE \u003cem\u003ecould not do\u003c/em\u003e. Further research is needed addressing this gap, which would help address the finding of substantial definitional fluidity regarding what activities do and do not constitute CE.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eAs this review highlights, CE is pivotal in addressing myriad challenges, such as distrust in healthcare systems, logistical barriers, and cultural resistance, by actively involving communities in vaccination initiatives. CE fosters trust, ownership, and local leadership, all of which are key to successful vaccination campaigns. Trust is particularly crucial in settings where historical injustices or a lack of transparency have created scepticism towards healthcare interventions. By involving community leaders and stakeholders, CE helps bridge the trust gap and ensures that vaccination efforts are perceived as locally driven rather than imposed by external entities. This sense of ownership, in turn, encourages communities to take an active role in supporting and sustaining vaccination efforts. Additionally, CE initiatives often focus on building local leadership capacities, which helps ensure that the community remains engaged and empowered even after the initial vaccination campaign has ended. This approach not only improves the immediate uptake of vaccines but also contributes to the long-term resilience of healthcare systems in these settings. Strategies that emphasize tailored communication, community participation, and collaboration with influential community leaders can significantly increase vaccine uptake and acceptance. Tailored communication involves adapting messages to align with local cultural norms and values, thereby addressing specific fears or misconceptions that may be prevalent within a community. This approach is particularly effective when combined with the use of trusted figures - such as religious leaders, teachers, or local healthcare workers - who can endorse vaccination and influence public opinion positively. Furthermore, CE initiatives that incorporate educational components help to demystify vaccines, providing communities with accurate information about vaccine safety, efficacy, and the importance of immunization in preventing disease outbreaks. These educational efforts can take various forms, including community meetings, door-to-door outreach, and the use of multimedia tools, all aimed at reaching diverse segments of the population.\u003c/p\u003e \u003cp\u003eOne of the primary takeaways from this review is the necessity for culturally sensitive, adaptable, and multi-faceted CE interventions. The findings indicate that a one-size-fits-all approach is inadequate, as each setting presents unique socio-cultural dynamics that must be understood and respected for vaccination campaigns to succeed. For instance, in some communities, gender dynamics may play a significant role in healthcare decision-making, necessitating targeted efforts to involve both men and women in CE activities. Successful interventions, such as the involvement of local leaders and use of trusted communication channels, show that culturally embedded strategies help build trust and address vaccine hesitancy more effectively. In settings where misinformation is widespread, engaging community influencers to counteract myths and provide factual information is essential. The involvement of respected community members helps to legitimize vaccination efforts, making them more acceptable to the broader population. Additionally, two-way communication channels were found to be essential, allowing for community feedback and real-time adjustments to vaccination campaigns, thereby enhancing their responsiveness and impact. Such channels ensure that the concerns of community members are heard and addressed, which not only improves trust but also allows health authorities to modify their approaches based on local needs and preferences. This adaptability is particularly important in crisis-affected settings, where conditions can change rapidly, and a flexible approach is needed to maintain the effectiveness of vaccination efforts. Moreover, the integration of mobile health technologies, such as SMS reminders, into CE interventions has proven effective in increasing vaccine coverage by providing timely information and reminders to caregivers, further illustrating the value of a multi-faceted approach.\u003c/p\u003e \u003cp\u003eThis review demonstrates a need for further research to better define and understand the components of CE in vaccination efforts, as has been previously reported [49]. A consistent theme across the studies was that CE is often vaguely defined and inconsistently applied. Future research should focus on unpacking the concept of CE, defining CE to include clear inclusion and exclusion criteria - what constitutes CE and what does not \u0026ndash; to help standardize CE interventions and allow for more rigorous evaluation of their impact. Additionally, creating a comprehensive list of CE interventions and categorizing them based on their effectiveness in different contexts will be vital. This classification can serve as a guide for practitioners, helping them select the most appropriate strategies for specific settings.\u003c/p\u003e \u003cp\u003eAnother crucial area for future research is measuring the effectiveness (and cost-effectiveness, as resources in humanitarian and low-income settings are often limited) of CE interventions. The development of an evaluation matrix that includes both qualitative and quantitative methods will be necessary to assess the impact of CE activities. This matrix should incorporate indicators such as coverage, timeliness, community attitudes, trust, vaccine hesitancy, and vaccine knowledge. By using tools like network analysis, researchers can better understand the relationships between different CE methods and their outcomes, ultimately identifying the most impactful approaches.\u003c/p\u003e \u003cp\u003eAn ongoing question in research on CE effectiveness is whether the contextual impact of CE can be measured, given that it is oriented towards creating an enabling environment for vaccine uptake, rather than directly distributing vaccines. Current evaluation approaches may need to explore the impact of CE from a social ecological assessment approach, rather than a traditional monitoring and evaluation approach. This question may be addressed through establishing a theory of change for CE in vaccine delivery, providing a valuable framework for understanding how CE activities contribute to desired outcomes, such as increased vaccine uptake and community resilience. This theory of change would map out the pathways through which CE influences vaccination efforts, from inputs and processes to outputs and outcomes. It would also highlight key assumptions and contextual factors that may affect the success of CE interventions, helping to identify areas where additional support or adaptation may be needed.\u003c/p\u003e \u003cp\u003eIn conclusion, CE is a powerful tool that can transform vaccine delivery efforts, particularly in vulnerable and underserved populations. By fostering local ownership, improving communication, and involving diverse community actors, CE helps bridge gaps in vaccine access and acceptance. Future vaccination strategies must prioritize and integrate CE as a core element, ensuring that communities are not merely recipients of interventions but active partners whose insights and leadership shape the design, implementation, and sustainability of public health efforts. Moving forward, refining the definition of CE, developing robust evaluation frameworks, and establishing a clear theory of change will be critical to maximizing the impact of CE in vaccination campaigns.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eWorld Health Organization. Vaccination in acute humanitarian emergencies: A framework for decision making. 2017. Available: https://www.who.int/publications/i/item/WHO-IVB-17.03\u003c/li\u003e\n\u003cli\u003eM\u0026eacute;decins Sans Fronti\u0026egrave;res. Refugee Health: An approach to emergency situations. 1997. Available: https://www.humanitarianlibrary.org/resource/refugee-health-approach-emergency-situations\u003c/li\u003e\n\u003cli\u003eSphere Project, editor. The Sphere Handbook: humanitarian charter and minimum standards in humanitarian response. Fourth edition. Geneva, Switzerland: Sphere Association; 2018. \u003c/li\u003e\n\u003cli\u003eUNICEF. 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Infect Ther. 2020;9: 421\u0026ndash;432. doi:10.1007/s40121-020-00302-9\u003c/li\u003e\n\u003cli\u003eOwoyemi A, Okolie EA, Omitiran K, Amaechi UA, Sodipo BO, Ajumobi O, et al. Importance of Community-Level Interventions During the COVID-19 Pandemic: Lessons from Sub-Saharan Africa. Am J Trop Med Hyg. 2021;105: 879\u0026ndash;883. doi:10.4269/ajtmh.20-1533\u003c/li\u003e\n\u003cli\u003eTilahun B, Mekonnen Z, Sharkey A, Shahabuddin A, Feletto M, Zelalem M, et al. What we know and don\u0026rsquo;t know about the immunization program of Ethiopia: a scoping review of the literature. BMC Public Health. 2020;20: 1365. doi:10.1186/s12889-020-09304-1\u003c/li\u003e\n\u003cli\u003eEngelbert M, Jain M, Bagai A, Parsekar SS. Improving routine childhood immunisation outcomes in low-income and middle-income countries: an evidence gap map. BMJ Open. 2022;12: e058258. doi:10.1136/bmjopen-2021-058258\u003c/li\u003e\n\u003cli\u003eGuillaume D, Am\u0026eacute;d\u0026eacute;e LM, Rolland C, Duroseau B, Alexander K. Exploring engagement in cervical cancer prevention services among Haitian women in Haiti and in the United States: a scoping review. J Psychosoc Oncol. 2022; 1\u0026ndash;20. doi:10.1080/07347332.2022.2154730\u003c/li\u003e\n\u003cli\u003eIsmail SA, Lam ST, Bell S, Fouad FM, Blanchet K, Borghi J. Strengthening vaccination delivery system resilience in the context of protracted humanitarian crisis: a realist-informed systematic review. BMC Health Serv Res. 2022;22: 1277. doi:10.1186/s12913-022-08653-4\u003c/li\u003e\n\u003cli\u003eJain M, Shisler S, Lane C, Bagai A, Brown E, Engelbert M, et al. Use of community engagement interventions to improve child immunisation in low- and middle-income countries: A systematic review and meta-analysis. Campbell Syst Rev. 2022;18: e1253. doi:10.1002/cl2.1253\u003c/li\u003e\n\u003cli\u003eJain M, Shisler S, Lane C, Bagai A, Brown E, Engelbert M. Use of community engagement interventions to improve child immunisation in low-income and middle-income countries: a systematic review and meta-analysis. BMJ Open. 2022;12: e061568. doi:10.1136/bmjopen-2022-061568\u003c/li\u003e\n\u003cli\u003eKaranja-Chege CM. HPV Vaccination in Kenya: The Challenges Faced and Strategies to Increase Uptake. Front Public Health. 2022;10: 802947. doi:10.3389/fpubh.2022.802947\u003c/li\u003e\n\u003cli\u003eMajekodunmi OB, Oladele EA, Greenwood B. Factors affecting poor measles vaccination coverage in sub-Saharan Africa with a special focus on Nigeria: a narrative review. Trans R Soc Trop Med Hyg. 2022;116: 686\u0026ndash;693. doi:10.1093/trstmh/trac013\u003c/li\u003e\n\u003cli\u003eAslam F, Yue Y, Jafri N, Babar Z-U-D. Research Evidence in Improving Vaccine Practices in Low and Middle-Income Countries: Examples of Community Engagement, Barriers, and Implementation Strategies. 2023. doi:10.1007/978-3-030-50247-8_144-1\u003c/li\u003e\n\u003cli\u003eNaidoo D, Meyer-Weitz A, Govender K. Factors Influencing the Intention and Uptake of COVID-19 Vaccines on the African Continent: A Scoping Review. Vaccines Basel. 2023;11. doi:10.3390/vaccines11040873\u003c/li\u003e\n\u003cli\u003eO\u0026rsquo;Rourke J, Yearwood A, Sheaf G, Tomsa S, Bianco V, Mosquera M, et al. What Works to Increase Uptake of Childhood Immunization: A rapid evidence assessment of the impact of interventions targeting caregivers, healthcare workers and communities. UNICEF; 2023. \u003c/li\u003e\n\u003cli\u003eOketch SY, Ochomo EO, Orwa JA, Mayieka LM, Abdullahi LH. Communication strategies to improve human papillomavirus (HPV) immunisation uptake among adolescents in sub-Saharan Africa: a systematic review and meta-analysis. BMJ Open. 2023;13: e067164. doi:10.1136/bmjopen-2022-067164\u003c/li\u003e\n\u003cli\u003eOyo-Ita A, Oduwole O, Arikpo D, Effa EE, Esu EB, Balakrishna Y, et al. Interventions for improving coverage of childhood immunisation in low- and middle-income countries. Cochrane Database Syst Rev. 2023;12: CD008145. doi:10.1002/14651858.CD008145.pub4\u003c/li\u003e\n\u003cli\u003eJain M, Duvendack M, Shisler S, Parsekar SS, Leon MDA. Effective interventions for improving routine childhood immunisation in low and middle-income countries: a systematic review of systematic reviews. BMJ Open. 2024;14: e074370. doi:10.1136/bmjopen-2023-074370\u003c/li\u003e\n\u003cli\u003eParsekar SS, Vadrevu L, Jain M, Menon S, Taneja G. Interventions addressing routine childhood immunization and its behavioral and social drivers. Front Public Health. 2024;12: 1364798. doi:10.3389/fpubh.2024.1364798\u003c/li\u003e\n\u003cli\u003eBain LE, Ngwayu Nkfusai C, Nehwu Kiseh P, Badru OA, Anne Omam L, Adeagbo OA, et al. Community-engagement in research in humanitarian settings. Front Public Health. 2023;11: 1208684. doi:10.3389/fpubh.2023.1208684\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"University of Geneva","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Community engagement, Vaccination, Developing Countries, Humanitarian Settings","lastPublishedDoi":"10.21203/rs.3.rs-6295865/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6295865/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eCommunity engagement (CE) is increasingly recognized as a critical strategy for enhancing vaccine delivery in low- and middle-income countries (LMICs) and humanitarian settings, yet the evidence base remains fragmented. This scoping umbrella review synthesizes findings from 24 reviews published between 2013 and 2024, spanning 56 countries, and addressing both routine and outbreak vaccination efforts. CE interventions were found to be consistently associated with improved vaccine acceptance, reduced hesitancy, and increased coverage, particularly in marginalized and hard-to-reach populations. Key mechanisms of success included community participation, two-way communication, local capacity strengthening, and culturally tailored education and outreach efforts. Trusted local actors played a pivotal role in promoting vaccine uptake by addressing misinformation and fostering trust. Interventions involving school- and home-based delivery, mobile technologies, and integrated strategies combining multiple CE components demonstrated the greatest effectiveness. Despite this, substantial definitional ambiguity around CE persists, leading to variation in implementation and evaluation. The review highlights the need for standardized frameworks to define, design, and assess CE in vaccine programs, emphasizing the importance of context-specific adaptation and inclusivity. Moreover, while CE is widely promoted, few studies explored its limitations or cost-effectiveness. In crisis-affected settings, where time and resources are constrained, early, targeted engagement with key community representatives can still foster local ownership and impact. CE must be understood not as an optional add-on, but as a core element of effective, equitable vaccination strategies. Future research should prioritize the development of operational definitions, theories of change, and robust evaluation tools to optimize CE\u0026rsquo;s impact on immunization outcomes.\u003c/p\u003e","manuscriptTitle":"Community engagement for vaccine delivery in low- and middle-income countries and humanitarian settings: A scoping umbrella review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-03-25 07:13:28","doi":"10.21203/rs.3.rs-6295865/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"0708cfcf-013e-4d5a-b2a9-863347a7bf91","owner":[],"postedDate":"March 25th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":46128271,"name":"Health Economics \u0026 Outcomes Research"}],"tags":[],"updatedAt":"2025-03-25T07:13:29+00:00","versionOfRecord":[],"versionCreatedAt":"2025-03-25 07:13:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6295865","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6295865","identity":"rs-6295865","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}