Submission ID 130434
| Issue/Objective | In 2024, 14.2 million children globally remain unvaccinated ("zero-dose (ZD) children"), exceeding the 2019 baseline of 12.9 million. As progress is off track to meet the Immunization Agenda 2030 (IA2030) target of a 50% reduction by 2030, intensified efforts are urgently needed. Reaching these children sustainably requires understanding and addressing the structural barriers that shape inequitable access to vaccination. We are conducting the second round of a living scoping review, updating the first 2020-2024 synthesis on ZD children in low- and middle-income countries to include studies up to 2026. |
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| Methodology/Approach | For the second round, we added Scopus to the databases used in the first round (MEDLINE, CINAHL, EBM Reviews, EMBASE, LILACS, Google Scholar), while maintaining the same inclusion criteria of peer-reviewed studies with quantitative evidence on ZD children. The second round is conducted in two phases: the first includes studies published up to August 2025, and the second includes studies published up to December 2026. Using Covidence©, two independent reviewers screened citations in a two-stage process and conducted data charting using a pre-tested form. Disagreements were resolved by consensus with senior reviewer input as needed. |
| Results | Preliminary findings are based on 47 articles from the 101 studies included in the first phase. Key barriers persist: low socioeconomic status (n=26), low maternal health service coverage (n=23), low maternal education (n=22), geographic constraints (n=16), and caregiver-related factors (n=14). Additional barriers include mobility-related challenges (n=18), weak system linkages (n=9), and connectivity gaps (n=4). Service delivery constraints are more clearly documented (n=17). Evidence on interventions is increasing, including studies targeting ZD children (n=5), in high-ZD settings (n=1), or reporting ZD-specific outcomes (n=6). Approaches include PHC integration (n=7), data-driven targeting (n=6), and community-based delivery (n=5). However, evidence on implementation, costs (n=2), and long-term impacts remains limited. |
| Discussion/Conclusion | Important evidence gaps remain on implementation, long-term impacts, and cost-effectiveness. However, the evidence base is evolving rapidly, with more studies expected by 2026. This presents a key opportunity to strengthen evidence on upstream determinants of inequity - including governance, health system constraints, and structural barriers - and to better inform equitable, system-level strategies to reach ZD children and their communities. |
| Presenters and Affiliations | Audrey Beaulieu École de santé publique de l'Université de Montréal (ESPUM) Esther Saville Gavi, the Vaccine Alliance Dan Hogan Gavi, the Vaccine Alliance Ziegler Daniela Centre Hospitalier de l'Université de Montréal (CHUM) Heidi W. Reynolds Independent Consultant Céline Thibeault Health Standards Organization (HSO) Gustavo C. Corrêa Independent Consultant Marion Perrot École de santé publique de l'Université de Montréal (ESPUM) Bangaman C. Akani École de santé publique de l'Université de Montréal (ESPUM) Joelle Ducharme École de santé publique de l'Université de Montréal (ESPUM) Mira Johri École de santé publique de l'Université de Montréal |
