Peer-reviewed article
Strengthening Primary Health Care Through Implementation Research: Strategies for Reaching Zero-Dose Children in Low- and Middle-Income Countries' Immunization Programs.
Oyugi B, Kallander K, Shahabuddin ASM ·
Summary
Written by AI, not yet AICS's view · claude-haiku-4-5-20251001This study synthesizes implementation research from 36 projects across 13 low- and middle-income countries to identify strategies for reaching zero-dose children who have never received any vaccination. The researchers examined 326 immunization strategies and found that most focused on strengthening primary health care through monitoring, workforce development, and models of care, with digital technologies playing an increasing role. Community engagement and governance emerged as critical enablers, though sustainable financing and private-sector involvement remained underdeveloped. The findings show that equity-driven strategies combining digital innovation, community engagement, and health system strengthening can improve immunization coverage, but reaching the hardest-to-reach children requires sustained progress on financing and governance.
Key points
- An estimated 14.3 million infants remained zero-dose in 2024, predominantly in low- and middle-income countries
- Of 326 immunization strategies identified, 76.1% aligned with operational primary health care levers, particularly monitoring and evaluation (19.3%), workforce development (18.7%), and models of care (12%)
- Community engagement (16.2% of improvements) and improved microplanning/data systems (23.5%) showed substantial impacts on service delivery
- Only 3 of 32 projects directly targeted zero-dose children, despite this being the stated priority
- Sustainable financing (3.4%) and private-sector engagement (0.9%) remain critically underdeveloped components of immunization programs
Limitations
The study does not specify which 13 countries were included or provide detailed outcome measurements for individual projects. It synthesizes multiple projects with varying designs and contexts, making it difficult to attribute specific coverage gains to particular strategies or to assess the generalizability of findings across different settings.
Abstract
Introduction: Despite global improvements in immunization, major gaps persist. By 2024, an estimated 14.3 million infants, predominantly in low- and middle-income countries (LMICs), remained zero-dose (ZD), never having received even the first DTP vaccine. In 2022, 33 million children missed their measles vaccination (22 million missed the first dose, 11 million missed the second dose), highlighting entrenched structural, behavioral, and systemic barriers that continue to exclude marginalized populations. Addressing these inequities requires innovative, context-adapted approaches that strengthen primary health care (PHC) and extend services to the hardest-to-reach populations. Objectives: This study aims to document and synthesize implementation research (IR) projects on immunization programs in LMICs, identifying key enablers and effective strategies that reduce inequities, improve outcomes, and support efforts to reach ZD children. Methods: We conducted a retrospective multiple-case study of 36 IR projects across 13 LMICs, embedded within an evidence review framework and complemented by policy analysis. Data were drawn from systematic document reviews and validation discussions with project leads. A total of 326 strategies were extracted, coded using a structured codebook, and mapped to the WHO-UNICEF PHC Levers for Action. Descriptive analysis synthesized patterns across service delivery and policy outcomes, including coverage gains, improved microplanning, community engagement, and system integration. Results: Of the 326 immunization strategies identified, most (76.1%) aligned with operational PHC levers, particularly monitoring and evaluation (19.3%), workforce development (18.7%), and models of care (12%). Digital technologies (11.7%) were increasingly deployed for real-time tracking and oversight. Core strategic levers comprised 23.9% of strategies, with community engagement (8.9%) and governance frameworks (7.7%) emerging as critical enablers, though sustainable financing (4%) and private-sector engagement (0.9%) were rarely addressed. While the majority of projects focused on routine immunization (n = 32), only a few directly targeted ZD children (n = 3). Interventions yielded improvements in both service delivery and policy outcomes. Improvements in microplanning and data systems (23.5%) reflected the increased uptake of digital dashboards, GIS-enabled tools, and electronic registries. Community engagement (16.2%) emphasized the influence of local leaders and volunteers in building trust, while health system strengthening (15.7%) invested in cold chain, supervision, and workforce capacity. Coverage gains (10.6%) were achieved through delivery innovations, though sustainable financing remained a critical problem (3.4%). Conclusions: Reaching ZD children requires equity-driven strategies that combine digital innovations, community engagement, and resilient system planning. Sustained progress depends on strengthening governance, financing, and research. Embedding IR in immunization programs generates actionable evidence, supports context-specific strategies, and reduces equity gaps, offering practical insights that complement health system research and advance the Immunization Agenda 2030.
Findings the Hub has extracted
Each claim below is labelled by its type of design and links back to this report.
- Intervention
- Multiple implementation research-driven strategies including digital technologies for tracking, improved microplanning and data systems, community engagement through local leaders and volunteers, health system strengthening (cold chain, supervision, workforce capacity), and governance frameworks
- Population
- Infants and children in immunization programs across 13 low- and middle-income countries; 36 implementation research projects
Key finding
Coverage gains of 10.6% achieved through delivery innovations
B et al. · Europe PMC · 9 Oct 2025