Factors affecting immunization coverage levels in a district of India

Abstract

Immunization coverage is measured to assess the performance of the Expanded Programme on Immunization. In 1988 we conducted a coverage survey among 12-23 month-old children in the North Arcot District (population 5 007 746) in southern India. In each of the 12 towns a 30-cluster sample survey was conducted. In the 35 rural blocks with 1590 panchayats, 159 were selected systematically and all children (n = 7300) were surveyed. In the towns, coverages ranged for measles vaccine from 29 to 53%, BCG from 65 to 91% and OPV and DPT third dose from just over 60% to just over 80%. In the rural areas, coverages ranged for measles vaccine from 10.8 to 19.3%, BCG 25.1-34.1%, DPT third dose 42.2-50.4% and OPV third dose 39.6-48%. In the towns, 25, 66, 67 and 59% of BCG, DPT, OPV and measles vaccines had been provided by private agencies showing that availability of vaccines throughout the week and easy access even in payment terms played an important role in achieving higher levels of coverage compared with rural areas where all vaccines are given by Government agencies, free of charge. In the rural areas, significantly large variations in coverage were seen among panchayats-large and peri-urban panchayats had significantly better coverage than small and more rural panchayats. Within any given block (the population unit consisting of 30-40 panchayats served by a Primary Health Centre), there were large variations in the levels of immunization coverage between panchayats. We believe that the variations in coverage levels in urban and rural areas and within rural areas reflect the efficiency of different immunization delivery systems or the staff themselves that serve such regions. Thus, neither the district nor the block is a satisfactory unit for coverage surveys, unless samples from areas stratified as towns and blocks and within blocks, panchayats stratified by their population size and proximity or distance from towns are selected. For detecting poorly immunized areas, information from each geographical area served by a health worker should be collected. As the system advances, coverage surveys should be replaced with auditing of immunization and also disease surveillance.