[National immunization day evaluation in Colombia, 2001: an ecological approach]

To determine OPV coverage impact of the 2001 national immunization day in different geographic regions and its association with the Unsatisified Basic Needs Index (NBI), forced displacement and armed conflict.

This is an analytical ecological study of multiple groups using multilevel observation units such as region, department, province and municipality. A bivariate analysis with difference between proportions between paired samples (McNemar test), estimation of OR, lineal regression and relative risk determination (Morgenstern) was carried out. In addition, protected and susceptible populations in each observation unit were compared.

The OPV3 coverage increase between October and December, 2001, was 15 to 19% (p<0.05) and the final coverage was 78-84%. The provincial analysis demonstrated a 25.8% of total population with OPV3 coverage greater than 95%. An increase of 4 to 7 departments and 281 to 328 cities with at least 95% coverage (p<0.05) was observed. The risk of having incomplete immunization schedules decreased in armed conflict zones, remained stable in areas with high NBI and increased in areas with a high proportion of displaced families. The booster goal of the OPV had reached a median of 61%.

The national immunization day diminished immunization access barriers for children under 5 years. The analysis of different geographic units controls the effect of the unknown population denominators. The ecological studies improved routine data analysis.