INTRODUCTION:
Malnutrition and vaccine-preventable diseases drive child mortality in humanitarian settings. Despite frequent contact points in routine immunisation, services often operate in silos. Aligned with the health without borders theme, this study evaluated the impact of two-way integration—incorporating nutrition into immunisation platforms or vice versa—to improve global health equity, coverage, and operational feasibility across static and mobile outreach models in resource-limited settings.

METHODS:
Following PRISMA guidelines, we searched five databases between January 2000 and January 2026. Twelve independent reviewers selected 47 studies, including RCTs, quasi-experimental, and mixed-methods designs. Interventions included same-day delivery of IYCF counselling, Vitamin A, therapeutic feeding, and Growth Monitoring and Promotion (GMP) alongside vaccines such as OPV and measles. Quality was assessed for all studies, and meta-analysis was performed using STATA to estimate pooled effect sizes.

RESULTS:
Evidence confirms two-way integration is feasible and significantly increases uptake. Meta-analysis revealed integrated IYCF counselling markedly improved exclusive breastfeeding rates (OR 2.91; 95% CI: 1.38, 6.16; p=0.005). Furthermore, integration significantly increased full immunisation coverage (OR 1.90; 95% CI: 1.59, 2.29; p<0.001) and facilitated identification of severe malnutrition while reducing zero-dose children in underserved communities. Mobile health teams in conflict-affected regions demonstrated high effectiveness for reaching displaced populations. However, a consistent fidelity gap emerged: technical tasks, particularly anthropometric measurements, were frequently omitted or inaccurate due to high patient volume and heavy staff workload.

CONCLUSIONS:
Two-way integration effectively maximises clinical contacts, advancing health equity in high-burden settings. As meta-analysis confirms substantial gains in breastfeeding and vaccination, the challenge has shifted from proof-of-concept to implementation fidelity. Findings support sustainable one-stop-shop models but highlight a critical need for simplified tools and standardised protocols. Future efforts should prioritise operationalising simplified delivery within primary healthcare systems rather than further small-scale pilots. Limitations include varying study quality and limited long-term sustainability data.