GIS-based accessibility analysis for immunization outreach planning in Ukraine

Background

Immunization is one of the most effective public health interventions. Targeting outreach immunization services remains challenging in conflict settings with population displacement, where practitioners often rely on convenience rather than data. Geographic accessibility is commonly used as a proxy for access to services and can support data-driven outreach planning. This study explores the use of GIS-based accessibility analysis to inform immunization planning in Ukraine, using Lvivska oblast as a pilot, given the high number of displaced population and diverse landscape.

Methods

We conducted a geospatial accessibility analysis using AccessMod 5. WorldPop estimates of children under five were combined with locations of immunization service points. Travel time to the nearest service was modelled under walking scenarios using land cover and road data, with speeds ranging from 1–4 km/h. Accessibility was calculated for 30, 60, 90, and 120-minute thresholds. Results were aggregated at hromada level. Assumptions and usefulness of outputs were tested with the Lvivska oblast.

Results

Overall, 31.2% of children lived beyond 30 minutes from services, decreasing to 3.5% beyond 120 minutes. However, disparities across hromadas were substantial, with up to 85.0% beyond 30 minutes in some hromadas and 42.7% beyond 120 minutes. Hromadas with a high share of population living beyond these thresholds should be prioritized for outreach. Pilot testing validated key assumptions and confirmed the approach’s usefulness, while also indicating that it could be further strengthened by integrating additional data, such as administrative coverage and cases.

Conclusions

GIS-based accessibility analysis is a useful tool for supporting data-driven outreach planning. However, as geographic accessibility is only a proxy for coverage, it should be used alongside other data sources. Further refinement, integrating other travel scenarios, and national scale-up are the planned next steps.

Key messages

• GIS accessibility analysis helps identify underserved populations and prioritize outreach immunization in conflict settings, moving planning from convenience-based to data-driven decisions.

• Accessibility alone is not enough; combining GIS outputs with other data improves usefulness for targeting outreach.