Cross-Border Vaccine Supply to Conflict-Affected Darfur: A Humanitarian Lifeline through Chad - An Implementation Case Study

Abstract Protracted conflict in Sudan since April 2023 has severely disrupted routine immunization services, particularly in the Darfur region, resulting in widespread vaccine stockouts, declining coverage, and increased risk of vaccine-preventable disease outbreaks. Traditional national supply routes became largely inaccessible, exacerbating inequities in immunization access for conflict-affected and displaced populations. This paper examines the design, implementation, and outcomes of a cross-border vaccine deployment strategy implemented in 2025 through Chad to restore vaccine availability in Darfur. Using programmatic data, shipment records, coverage reports, and partner monitoring outputs, the study assessed the operational feasibility, partnership arrangements, and public health impact of the intervention on routine immunization and outbreak response. In 2025, nearly 20 million doses of vaccines were successfully delivered to the five Darfur states through cross-border operations, supporting routine immunization services and outbreak response campaigns. Average coverage for the first dose of a DPT-containing vaccine (DPT1) increased from 22.6% in 2024 to 83.2% in 2025, while DPT3 and MCV1 coverage rose to 55.4% and 50.4%, respectively. Oral cholera vaccine campaigns achieved 90.4% coverage among targeted populations, and polio outbreak response campaigns exceeded 100% administrative coverage, reflecting both successful reach and uncertainties in target population estimates due to population displacement. Investments in cold chain infrastructure and strengthened coordination among government, UNICEF, Gavi, and implementing partners were critical to these outcomes. The findings demonstrate that cross-border vaccine deployment can serve as a viable and effective mechanism for restoring immunization availability and support recovery of immunization service delivery in a highly constrained conflict setting. While not a substitute for functional national systems, such approaches are essential life-saving interventions during acute crises and should be integrated into preparedness planning for fragile and conflict-affected contexts.