Background: Data aggregation in national information systems begins at the district level. Decentralization has given districts a lead role in health planning and management, therefore validity of administrative-based estimates at that level is important to improve the performance of immunization information systems.
Objective: To assess the validity of administrative-based immunization estimates and their usability for planning and monitoring activities at district level.
Methods: DTP3 and measles coverage rates from administrative sources were compared with estimates from the EPI cluster survey (ECS) and Demographic and Health Survey (DHS) carried out in 2003 at national and regional levels. ECS estimates were compared with administrative rates across the 52 districts, which were classified into three groups: those where administrative rates were underestimating, overestimating or concordant with ECS estimates (differences within 95% CI of ECS rate).
Results: National rates provided by administrative data and ECS are similar (74% and 71% for DTP3 and 68% and 66% for measles, respectively); DHS estimates are much lower. Regional administrative data show large discrepancies when compared against ECS and DHS data (differences sometimes reaching 30 percentage points). At district level, geographical area is correlated with over- or underestimation by administrative sources, which overestimate DTP3 and measles coverage in remote areas. Underestimation is observed in districts near urban and highly populated centres. Over- and underestimation are independent of the antigen under consideration.
Conclusions: Variability in immunization coverage across districts highlights the limitations of using nationally aggregated indicators. If district data are to be used in monitoring and planning immunization programmes as intended by decentralization, heterogeneity in their validity must be reduced. The authors recommend: (1) strengthening administrative data systems; (2) implementing indicators that are insensitive to population mobility; (3) integrating surveys into monitoring processes at the subnational level; (4) actively promoting the use of coverage information by local personnel and district-level staff.