Using the DSF as a heuristic device, in what follows we firstly describe the findings from our pre-campaign phase’s assessment, which helped in characterising Madagascar’s ecological context and practice setting in relation to the intervention. We then describe the initial strategy (Phase 1) in light of the findings of the earlier assessments. This is followed by a summary of the findings from the process evaluation, which prompted key adaptations of the initial strategy (Phase 2). Finally, we present the results from our outcome evaluation (Fig. 1). The interventions operated at each site, in terms of logistics and infrastructure, workforce, community engagement, and stakeholder collaboration, all of which are summarised in Table 1.

Table 1 Summary of interventions operated at each vaccination sitePre-campaign phaseCharacteristics of the ecological system and practice setting

Our territorial assessment allowed to identify two main scenarios in terms of available infrastructures: (i) CSBs appropriately resourced to perform a vaccination campaign, (ii) functional health structures for storage of vaccines and waste disposal, (iii) CSBs that required infrastructural intervention to allow the conduct of the campaign. The main elements identified as barrier for the campaign were related to a stable electricity supply that would impact directly both storage and delivery of the vaccines. Among the infrastructures evaluated, we found no barriers for the implementation of the campaign in the CSBs of the districts of Mahajanga I and II, Mitsinjo, and Soalala. The vaccinodrome at the DRSP in Mahajanga I and the CHU Pzaga were selected as central facilities to store vaccines and to operate the waste disposal respectively. For waste disposal, minor interventions were needed to be put in place, e.g., while the CHU Pzaga was already sufficiently equipped the facility had not been operational. Finally, the CSBs of the districts of Marovoay and Ambato-Boeny required infrastructural interventions in order to guarantee adequate vaccine delivery. Some of the areas for improvement identified in terms of supply management, included inefficiencies in tracking inventory lists, maintaining equipment, and overseeing management practices. Findings from stakeholder meetings, KII and discussions with community members collectively shed light on various ecological aspects related to both direct elements of vaccine administration, such as insufficient medical devices, staffing shortages, inadequate quality control measures and, lack of user-friendly data collection tools at vaccination hubs, as well as those more related to the surroundings such as the possibility to reach remote locations, community beliefs, and attitudes towards healthcare. Insights gleaned from discussions with policymakers underscored critical ecological considerations, highlighting the imperative to enhance sanitary waste disposal and bolster pharmacovigilance preparedness.

Through a community-based survey, we assessed COVID-19 vaccine awareness as well as common sources of information, and attitudes towards vaccination. A total of 854 participants aged 18 years or more were recruited in the first wave of the COVID-19 vaccine awareness survey, 48.1% male and 51.9% female. Participants’ characteristics are summarized in Table S1 (Additional file 1).

Prior to CoBoGo, the population level of awareness about COVID-19 in the Boeny region had been high, with 86.5% of survey respondents reporting to have heard or seen news about COVID-19 vaccines, and 78.8% stating that they know where to get accurate information about COVID-19 vaccines (Fig. 2). The survey identified CHWs (42.2%), Radio (41.9%), and TV (39.0%) as the most frequently used trusted sources of information about vaccines among the population. Only 5.0% of participants considered social media as a reliable source of information on COVID-19 vaccination. More than half of the respondents (54.9%) reported to have received enough information about COVID-19, while 34.3% perceived the amount of information received as not enough, while 10.8% stated to have received too much information.

Fig. 2

Population awareness, vaccine hesitancy, and perceptions regarding COVID-19 prior to the CoBoGo campaign

Among the unvaccinated participants, 54.3% of the respondents expressed concerns about contracting COVID − 19, and 70.1% considered COVID − 19 to be a severe disease. However, 50.4% of the respondents reported to be hesitant towards COVID-19 vaccinations. Levels of vaccine hesitancy varied among population subgroups. Female sex (aPR = 1.31, CI 95%:1.13; 1.56), higher education (aPR = 1.29, CI 95%: 1.01; 1.64), lack of trust in health authorities (aPR = 1.52, CI 95%: 1.30; 1.78), low perceived risk of contracting COVID-19 (aPR = 1.50, CI 95%: 1.24; 1.80), perceived low severity of the COVID-19 disease (aPR = 1.41, CI 95%: 1.15; 1.73) were associated with higher vaccine hesitancy (Table S2, Additional file 1).

Discussions with community members gave further insights into potential barriers of vaccine acceptance within the communities, such as the influence of the infodemic, and rumours about the efficacy of the vaccine, and adverse effects. Additionally, they allowed us to identify suitable modalities for vaccination delivery, such as through mobile units at marketplaces.

Phase 1: initial strategy – key adaptations to the standard approach

Based on the elements that were identified by both the qualitative and quantitative pre-campaign assessment data, an initial strategy was designed to start the vaccination. Key adaptations to the standard approach implemented prior to the campaign were organised into three main pillars, addressing respectively (i) logistics and supply, (ii) awareness raising initiatives, and (iii) re-organization of medical staff.

The first pillar covered initially those CSBs, that required infrastructure enhancement. These were capacitated through the installation of solar generators to mitigate energy instability. Additionally, a standardized supply management system was implemented, including the introduction of a material inventory, and a quality management system, incorporating user-friendly tools, such as site-specific material lists and weekly consumption tables, which seamlessly integrated into the routine of the CSBs.

As part of the second pillar, an awareness raising initiative was implemented. A total of ten radio spots were designed by 14 community ambassadors, selected from among youth champions engaged within local activist groups, such as students, scouts, religious, and women’s associations. The DRSP Health Promotion Department revised and approved the messages that were delivered through three radio stations five times per day for a total of 20 weeks.

The ambassadors played an essential role in our participatory approach, which formed the basis of our campaign. After an exchange session, including definition of needs by the community and targeted trainings to address the communication with the community, the ambassadors promoted the vaccination campaign through community-based initiatives, such as university football matches, festivals, and market days. They additionally coordinated their work with CHWs in mobilizing community members to produce a snowball effect of the campaign by which every member of the community was simultaneously recipient and deliverer of the campaign through community meetings and door-to-door visits.

Finally, the third pillar involved an adapted team organization for the delivery of the vaccines in order to optimize the use of human resources both in terms of roles, specific expertise, and knowledge of the territory. Specifically, three doctors were assigned coordinating roles based on their expertise and areas of focus. One doctor oversaw vaccination activities, collaborating closely with the DRSP and CSB2 chiefs to ensure adherence to SOPs and alignment with the DRSP’s EPI. Another doctor coordinated rural sites, overseeing awareness initiatives, and vaccination activities whilst conducting regular monitoring visits to ensure well-equipped facilities and effective waste management. A third doctor led the awareness team, comprised of Malagasy ambassadors and CHWs, who facilitated communication and collaboration among team members to maximize the impact of the awareness campaigns.

Campaign process evaluation

Informed by the principles of the DSF, we implemented a comprehensive process evaluation that unfolded throughout the entirety of the campaign. This evaluation involved continuous monitoring, discussion, and adaptation of the campaign’s implementation process. Weekly multi-sectoral stakeholder meetings facilitated collaboration between CSBs chiefs, and healthcare providers fostering coordinated efforts to address challenges such as vaccine hesitancy and misinformation. During the Pre-campaign Phase and between Phase 1 and 2, VDC needs assessments revealed critical gaps in vaccine distribution infrastructure, emphasizing the urgent need for improved transportation and additional medical devices, such as vaccine carriers to effectively reach remote areas. As a result of these assessments, we recognized the necessity to adapt our strategy. Problem-solving meetings involving core staff and stakeholders led to innovative solutions for logistical challenges, such as a community-led awareness campaigns and the introduction of mobile vaccination clinics in Phase 1, and their expansion, in terms of number of initiatives, during Phase 2. The ongoing monitoring of outcome indicators allowed for real-time assessments of the campaign’s progress, enabling us to identify areas where strategy adjustments were necessary to optimize vaccine coverage and address emerging issues throughout the project’s life cycle.

Phase 2: key adaptations

Informed by the comprehensive process evaluation conducted throughout the campaign, we not only made several key adaptations during the initial phase of the campaign, but also within each implementation pillar as we transitioned into Phase 2.

Logistics and infrastructure

Recognizing logistical hurdles in vaccine transportation and infrastructural needs, we increased frequency of vaccine distribution activities from biweekly in Phase 1 to daily in Phase 2. This involved extending transportation to ensure access to remote areas and providing additional vaccine carriers. In Phase 2, the advanced strategy was extended to include four additional CSBs in Mahajanga II (Belobaka and Boanamary,) and two in Ambato-Boeny (Andranofasika and Tsaramandroso).

Community engagement

Continuation of community-led awareness campaigns in Phase 2, due to their successful implementation in Phase 1.

Stakeholder collaboration

Leveraging the success of weekly multi-sectoral stakeholder meetings in fostering collaboration between CSB chefs and healthcare providers, these too were continued without significant changes in Phase 2.

Health workforce strengthening

Responding to the need for increased human resources in the rural sites, we deployed a higher number of CHWs for awareness-raising activities during Phase 2.

By aligning our adaptations with the pillars identified through our continuous process evaluation, we ensured a responsive approach in addressing challenges as they arose, and to optimize vaccine coverage.

Campaign indicators: outcome evaluationDistribution of vaccine doses

During the CoBoGo campaign, a total of 566 outreach activities were conducted, and a total of 24,888 COVID-19 vaccine doses administered, 19,338 first doses and 5550 boosters, ranging from 2684 to 8759 doses per month (Fig. 3, panel A). The distribution of doses by sex was balanced, 49.4% for male vs 50.6% for female (Fig. 3, panel B). Of all the vaccine doses, 50.5% were administrated in Mahajanga, 23.6% in Marovoay, 14.4% in Mahajanga II, and 11.6% in Ambato-Boeny (Fig. 3, panel C). The CoBoGo campaign mostly reached middle-aged and young individuals, the majority of the vaccinated were 25–49 years old (48%) and 18–24 years old (34%), while only 9.5% and 8.5% of doses were distributed among 50–59 and 60 + years old, respectively (Fig. 3, panel D).

Fig. 3

Distribution of COVID-19 vaccine doses deployed during the CoBoGo campaign. Legend: A Cumulative monthly number of 1st doses and booster vaccine doses, B Distribution of doses by sex, B Distribution of doses by region, B Distribution of doses by age group

Comparison between Phase 1 and Phase 2

Comparing the performance of the CoBoGo campaign in first trimester of 2023 to a previous standard approach implemented in the first trimester of 2022, we observed a considerable increase in the number of administered doses in the CSB2s of Mahajanga I (Tanambao Sotema, Mahavoky Sud and Tsararano Ambony) and more than a 2.2-fold increase in Marovoay (Morafeno, Antanambao and Ankazomborona) (Fig. 4).

Fig. 4

Comparison of CoBoGo campaign (2023) vs. standard approach (2022) in first trimester vaccine deliveries

Comparing the performance of the CoBoGo campaign following the implementation of Phase 2 vs. Phase 1 we observed a statistically significant change in trend, with an 8% increase in the number of weekly administered doses (RR = 1.08, CI 95%: 1.01; 1.15) (Fig. 5). Baseline trend (RR = 1.02, CI 95%: 0.96; 1.08) and change in level (RR = 1.38, CI 95%: 0.89; 2.12) were not statistically significant (Table S3 Additional file 1). We estimated that under the hypothetical scenario without implementation of the adapted strategy of Phase 2 between weeks 16 and 26, only 7184 vaccine doses would have been delivered to the population, while with our adaptation we were able to deliver 16,815 COVID-19 vaccines.

Fig. 5

Weekly COVID-19 vaccine deployment trends: CoBoGo Phases 1 and 2

Awareness campaignVariability of vaccine awareness and hesitancy outcomes

A total of 1034 participants aged 18 years and older were recruited into the second COVID-19 awareness survey wave. Participants’ characteristics are summarized in Table S1 (Additional file 1). No significant changes in COVID-19 vaccine awareness were observed at population level after the CoBoGo campaign. The proportion of awareness was 86.4% in the second survey wave, compared to 86.5% in the first wave (\(\Delta\)=0.003, CI 95%: −0.03; 0.04) (Fig. 6). For the unvaccinated population, the level of vaccine hesitancy remained high, following CoBoGo, 50.6% of unvaccinated respondents reported to be hesitant to get vaccinated against COVID-19 in the second survey wave, compared to 50.4% estimated at baseline, (\(\Delta\)=0.02, CI 95%: −0.04; 0.08). In contrast, the proportion of those who knew where to get accurate information on COVID-19 vaccination increased after CoBoGo, from 78.8% to 82.7% (\(\Delta\)=0.04, CI 95%: 0.003; 0.08).

Fig. 6

Change in outcomes (\(\Delta [\text95])\) following CoBoGo vaccination campaign implementation. Legend: **Model adjusted for sex, age group, urbanization, education, occupation, perceived financial situation during the COVID-19 pandemic, living with children under 5, concerns about contracting COVID-19, perceived severity of COVID-19 infection, and trust in health authorities

Radio (42.8%), TV (38.1%) and CHWs (48.8%) remained the most frequently mentioned sources of information on COVID-19 vaccines, however, the proportion of the population recognizing CHWs as the most reliable source of information increased (△=0.07, CI 95%: 0.02; 0.12). Population perceptions regarding the amount of available information also changed over time: the proportion of those not receiving enough information on COVID-19 decreased from 34.3% to 24.1%, (△=-0.11, CI 95%: -0.15; -0.07), whereas the proportion of those who reported to have received too much information increased from 10.8% to 37.7% (△=0.29, CI 95%: 0.25; 0.33) (Fig. 6).

Sustainability outcomesStaff trained

A total of 340 health care staff were trained in topics and research methodologies related to vaccines and vaccination. A total of 260 CHWs were trained on awareness-raising strategies. The 42 health care workers permanently employed by the regional vaccination program were trained in vaccine administration and management of adverse events following immunization as well as in safety procedures and quality management of the stock. Twenty-four interviewers and six researchers were trained in research methods and primary qualitative and quantitative data. Finally, a total of 14 young ambassadors selected to engage communities through peer communication, were trained in addressing communication issues to mitigate rumours and the infodemic. All of the CHWs and vaccination program team, such as vaccine administrators and nurses, were permanently employed by the MoH. All other staff members were selected from a pool of non-permanent staff within the region as identified by local stakeholders. One advantage of training both MoH and local staff is that both are available for future implementation initiatives and operational research projects.

Facilities equipped

A total of 12 governmental facilities were equipped and refurbished. Of those, 10 were at primary level of care (CSBs). The specific interventions operated included the reinforcement of the power and cold chain through the installation of solar panels and −80°C freezers, the structure of the waste management at both decentralised and central level so as the introduction of tools for the weekly supply monitoring to mitigate stockouts. Additionally, equipment for mobile vaccination hubs, designed to be sustainable and versatile, was supplied for placement in CSBs and outreach activities. All materials were sourced from local manufacturers and allocated to the DRSP’s EPI at the project’s conclusion to sustain ongoing activities.

SOPs and awareness raising material

A total of four SOPs were established in the frame of the campaign in collaboration with the Boeny DRSP’s EPI. These addressed: 1. vaccination procedures, 2. adverse event management, 3. pharmacovigilance, and 4. the implementation of sanitary waste disposal. They have been formally integrated within the vaccination plan of the Boeny DRSP’s EPI.

In addition, a collection of information material, including visual and audio messages, were archived within the Health Promotion Department of the DRSP of Boeny upon direct validation by the MoH. A clear workflow was created to build and validate awareness-raising content, which can be sustainably reused for future initiatives.