Over the past five decades, global immunization efforts have saved millions of lives, with low- and middle-income countries (LMICs) benefiting substantially. Nevertheless, major gaps in childhood vaccination coverage persist. In 2024, an estimated 14.3 million infants worldwide were classified as zero-dose children, meaning that they had not received the first dose of a diphtheria, tetanus, and pertussis-containing vaccine (DTP1). Children in fragile, conflict-affected, displaced, and other underserved settings may face particularly severe barriers to routine immunization. Their vulnerability reflects interconnected barriers involving access to health services, the reliability of vaccine delivery and supply systems, and caregivers’ knowledge, confidence, and willingness to vaccinate.
A recent scoping review of experimental and quasi-experimental studies conducted between 2000 and 2024 identified three interconnected domains for improving childhood immunization in LMICs: access to vaccination services, delivery systems and logistics, and health literacy and caregiver acceptance. The evidence suggests that interventions targeting individual barriers can improve specific outcomes, but more consistent and sustained improvements were observed when supply-side and demand-side strategies were implemented in combination.
Improving access focuses on reducing the physical, economic, and organizational barriers that prevent children and families from reaching vaccination services. Geographic distance, transportation costs, weak health infrastructure, and last-mile challenges remain important obstacles, particularly in underserved communities. Approaches associated with improvements included decentralized planning and microplanning, health-system strengthening,community health worker engagement, community outreach, financial incentives, and digital reminder and recall systems. These interventions can improve vaccination coverage, completion, and timeliness, but their effectiveness depends on factors such as implementation capacity, data quality, and integration with routine health services.
Delivery systems and logistics address a different but equally important challenge: ensuring that vaccines are reliably available when and where children receive care. Weaknesses in cold-chain management, transportation, storage capacity, electricity supply, and inventory systems can compromise vaccine availability and lead to stock-outs and missed vaccination opportunities. Supply-chain optimization has improved vaccine availability, distribution efficiency, and stock management in several settings. However, stronger logistics alone may not lead to higher vaccination coverage if families continue to face access barriers or lack confidence in vaccination. Emerging technologies, including drone-assisted delivery, may help address last-mile challenges, but their long-term value depends on alignment with existing health-system capacity and governance.
On the demand side, caregivers’ vaccination decisions are shaped by knowledge, safety concerns, misinformation, trust, social influences, and practical constraints. Educational interventions including home visits, participatory training, digital communication, and reminder systems have improved vaccine knowledge, confidence, coverage, and timeliness in different settings. Approaches using culturally responsive communication, trusted community actors, and supportive, confidence-building messages have been associated with more durable improvements in vaccine acceptance and completion, whereas fear-based or loss-framed messaging may undermine trust and discourage vaccination..
Overall, childhood immunization in LMICs depends on the alignment of supply-side readiness and demand-side engagement. Reliable vaccine delivery is necessary, but it cannot ensure high coverage when services remain physically or economically inaccessible or when caregivers lack trust. Conversely, efforts to increase demand are unlikely to succeed when vaccines or services are unreliable. Sustainable and equitable improvements therefore require integrated strategies that strengthen supply chains, reduce barriers to access, support community-based service delivery, and build trust through culturally responsive communication embedded within routine health systems.
Relevant Research:
1. Fatinah Y, Qolbina M, Alfaqeeh M, et al. Childhood immunization barriers and interventions in low- and middle-income countries: A scoping review of access, delivery systems, and health literacy. Human Vaccines & Immunotherapeutics. 2026;22(1):2651508. doi:10.1080/21645515.2026.2651508
2. World Health Organization & UNICEF. Global childhood vaccination coverage holds steady, yet over 14 million infants remain unvaccinated. Joint news release, 15 July 2025. https://www.who.int/news/item/15-07-2025-global-childhood-vaccination-coverage-holds-steady-yet-over-14-million-infants-remain-unvaccinated-who-unicef
3. Delavande A, Shahab A, Younas J, Zafar B. Improving childhood immunization through maternal support: Evidence from a randomized intervention in Pakistan. Journal of Development Economics. 2026;182:103808. doi:10.1016/j.jdeveco.2026.103808
Translating and summarizing: Tianyi Deng
Reviewer: Ziqi Liu
Page Editor: Ruitong Li
