Why caregivers start but do not finish: a qualitative evidence synthesis of barriers and facilitators to malaria vaccine dose completion in sub-Saharan Africa

Technical Summary: Why Caregivers Start but Do Not Finish: A Qualitative Evidence Synthesis of Barriers and Facilitators to Malaria Vaccine Dose Completion in Sub-Saharan Africa

Problem Statement
Two World Health Organization (WHO)-recommended malaria vaccines, RTS,S/AS01 and R21/Matrix-M, are being introduced across sub-Saharan Africa on a multi-dose schedule. While coverage for the primary series (three doses) is comparatively high (approximately 70–75%), a substantial proportion of children do not return for the later booster dose (the fourth dose), with completion rates often falling below 50%. Existing systematic reviews on this topic are quantitative; they measure the proportion of caregivers who accept the vaccine but fail to explain why those who initiate the series do not complete it. There is a distinct lack of qualitative evidence synthesis addressing caregiver-level determinants of dose completion, leaving programmatic gaps in understanding the "fall-off" between the primary series and the final dose.

Methodology
This study is a qualitative evidence synthesis conducted in accordance with the Enhancing Transparency in Reporting the Synthesis of Qualitative Research (ENTREQ) statement.

• Search Strategy: Four databases (PubMed, Scopus, CINAHL, African Journals Online) were searched from 2019 to June 23, 2026.
• Eligibility: Studies were selected using the SPIDER framework. Inclusion criteria required primary qualitative or mixed-methods studies focusing on caregiver perspectives regarding malaria vaccine uptake or completion in sub-Saharan Africa. Studies were excluded if they were purely quantitative, focused solely on health worker/policymaker perspectives, or concerned non-malaria vaccines.
• Data Sources: From 86 identified records, 13 studies met the inclusion criteria, providing 11 independent data sources from Ghana, Kenya, Malawi, Cameroon, Uganda, Nigeria, Sudan, and Sierra Leone.
• Analysis: Two reviewers independently screened, coded, and appraised studies using the Critical Appraisal Skills Programme (CASP) checklist. Thematic synthesis followed the three-stage approach of Thomas and Harden (line-by-line coding, descriptive themes, analytical themes).
• Confidence Assessment: The confidence in findings was assessed using the GRADE-CERQual approach, considering methodological limitations, coherence, adequacy, and relevance.

Key Contributions and Results
The synthesis generated three analytical themes explaining the divergence between vaccine initiation and completion:

1. Earned Confidence (High Confidence):
   Caregivers do not necessarily begin the series due to detailed prior knowledge, but rather due to trust in the health system and frontline workers. This trust is reinforced over time as caregivers observe a visible reduction in malaria episodes in their children following the early doses. Acceptance is described as "earned" and grows from provisional trust to conviction based on observed efficacy.

2. Premature Satisfaction (Moderate Confidence):
   Completion is often eroded not by active refusal, but by a "quiet drift." Caregivers who see their children protected after the early doses may conclude the child is already safe, rendering the final dose unnecessary. This sentiment is compounded by the schedule structure: the final dose occurs 12–18 months after the primary series, often outside routine immunization contact points, leading to forgetfulness or deprioritization. Additionally, the perception of the four-visit schedule as excessive contributes to dropout.

3. Willing but Blocked (Moderate Confidence):
   A significant group of caregivers intends to complete the schedule but is prevented by external barriers. These include:

   • Health System Factors: Disrespectful or scolding provider behavior, strikes, stockouts, and service closures.
   • Practical Barriers: Travel costs, distance to facilities, and migration out of pilot implementation areas where the vaccine is unavailable.
   • Household Dynamics: Decision-making authority often rests with partners or elders; a willing mother may be blocked from returning if the household head disapproves.

Significance and Claims
The paper claims that the central determinant of dose completion is not the initial acceptance of the vaccine, but the ability of the health system, the schedule, and the household to sustain the caregiver across the long interval between doses.

• Reframing the Problem: The synthesis argues that high initial acceptance rates (as seen in quantitative surveys) do not guarantee completion because the drivers of initiation (trust, initial education) differ from the drivers of completion (sustained engagement, structural alignment, household support).
• Programmatic Implications: The authors assert that interventions must shift from securing initial acceptance to supporting completion. Specific recommendations derived from the evidence include:
  • Aligning the final dose with existing immunization contacts (e.g., rescheduling to 18 months to coincide with routine visits).
  • Implementing late-schedule reminders and defaulter tracking to counter "quiet drift."
  • Training frontline workers in respectful communication to prevent deterrence.
  • Engaging household decision-makers (partners/elders) alongside mothers to remove internal barriers.
  • Explicitly communicating that early protection (after 3 doses) is not full protection to counter premature satisfaction.

The study concludes that while caregivers are generally willing and motivated, completion is eroded by premature satisfaction, structural misalignment of the schedule, and systemic/household barriers. The primary contribution is identifying these specific mechanisms to inform program design that sustains caregivers through the full vaccine schedule.