Distance and Coverage Geospatial Analysis of Routine vs Campaign Immunization in Sindh, Pakistan

Abstract Background The Zindagi Mehfooz Electronic Immunization Registry (ZM-EIR) has improved immunization coverage tracking in Sindh, Pakistan. However, to address missed vaccinations in underserved areas, the government launched the Big Catch-up campaign (BCU). Integrating ZM-EIR data with geospatial techniques allows for assessing and tracking immunization services in these areas. This study evaluates the impact of BCU campaign on immunization coverage, spatial disparities and track vaccinators’ reach by leveraging geospatial techniques. Methods We analyzed Penta-1 and Measles-1 vaccination data of children aged 0-5 years from October 21 to December 16, 2024, categorized into routine immunization (October 21-November 18) and BCU campaign (November 19-December 16) periods. Using geospatial analysis, we identified low coverage areas, compared immunization coverage, and assessed proximity to nearest immunization centers during both periods. Results Comparison showed a significant increase of 49.8% (230,967/464,140) in total coverage, with Penta-1 and Measles-1 coverage increased by 59.1% (129,531/219,033) and 41.4% (101,436/245,107), respectively. Additionally, with implementation of targeted strategies on identified hotspot results showed noticeable coverage improvement. 20 out of 30 districts had coverage below 31%, based on the BCU target, which improved by more than 50% during the BCU campaign. The mean distance from nearest immunization center to immunization event was 0.33 km higher for BCU outreach in contrast to routine outreach, reflecting slight expansion of outreach efforts during BCU campaign. Conclusions This study shows significant impact of BCU campaign's on low coverage areas. The findings reveal significant increases in Penta-1 and Measles-1 vaccinations and highlight spatial disparities in immunization access. Geospatial techniques proved useful in identifying underserved areas and tracking outreach efforts, supporting effective immunization strategies. Key messages • The big Catch-Up campaign increased immunization in Sindh, coverage increased by 59.1% for Penta-1 and 41.4% for Measles-1, showing significant increase in low performing districts. • Geospatial analysis with integrating ZM-EIR data allow to identify underserved areas and track outreach services, aiding more targeted and effective immunization strategies.