Geospatial analysis finds major immunization access gaps in South Sudan’s Unity State
Nearly six in 10 children under age 5 in South Sudan’s Unity State live beyond a one-hour travel time from routine immunization services, according to a World Health Organization analysis that highlights major geographic barriers to childhood vaccination.
The analysis found that only 42% of the under-five population studied can reach routine immunization services within one hour under the current distribution of health facilities, leaving about 69,000 children — or 58% — beyond the accessibility threshold.
The assessment is part of the WHO South Sudan Knowledge Management Series for Health and uses geospatial intelligence to identify underserved communities and guide more equitable immunization planning. It focuses on Unity State, where dispersed settlements, seasonal flooding, limited transport infrastructure and insecurity can restrict access to health services.
The analysis covered the Greater Upper Nile region, including Unity, Jonglei and Upper Nile states, with Unity selected as a case study because of its significant geographic accessibility challenges. Researchers used a one-hour travel-time threshold and analytical platforms including AccessMod, ArcGIS Pro and QGIS.
The findings show that 46% of mapped settlements in Unity State are located more than one hour from the nearest routine immunization service. The greatest constraints were identified in Rubkona, Koch and Guit counties, where dispersed settlements, seasonal flooding and limited service availability contribute to poor access.
Seasonal conditions also have a significant effect. The modelling found an average 18% gap in immunization coverage between dry- and wet-season conditions, demonstrating how flooding and other environmental barriers can disrupt access to routine services.
The study found that strategic optimization of service delivery locations could increase accessibility from 42% to 65%, potentially reaching an additional 26,409 children.
Researchers said the findings demonstrate the value of using geospatial analysis to move immunization planning beyond administrative boundaries and facility locations and instead assess whether communities can realistically reach services.
The approach combines population, health facility, transportation, hydrography and environmental data to model travel times under dry- and wet-season conditions. It then assesses coverage, identifies underserved populations and evaluates options for optimizing service locations.
The analysis also points to opportunities for using existing health infrastructure more effectively. Strategic placement of routine immunization services at selected facilities could improve system performance without relying solely on the establishment of new service delivery points.
For communities that remain difficult to reach, the report recommends targeted outreach, mobile vaccination services and stronger community engagement to improve service utilization.
The WHO analysis recommends institutionalizing accessibility assessments in routine immunization microplanning and annual planning, prioritizing counties and payams with the largest accessibility and seasonal gaps, and using optimization analysis to guide investments in existing health facilities.
It also calls for regular updates of geospatial datasets to track changes in population distribution, service availability and accessibility, and recommends scaling the approach nationally to support data-driven immunization planning across South Sudan.
