FACTORS AFFECTING IMMUNIZATION COVERAGE LEVELS IN A DISTRICT OF INDIA

Immunization coverage is measured to assess the performance of the Exp anded Programme on Immunization. In 1988 we conducted a coverage surve y among 12-23 month-old children in the North Arcot District (populati on 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 panchaya ts, 159 were selected systematically and all children (n = 7300) were surveyed. In the towns, coverages ranged for measles vaccine from 29 t o 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 v accine from 10.8 to 19.3%, BCG 25.1-34.1%, DPT third dose 42.2-50.4% a nd OPV third dose 39.6-48%. In the towns, 25, 66, 67 and 59% of BCG, D PT, OPV and measles vaccines had been provided by private agencies sho wing that availability of vaccines throughout the week and easy access even in payment terms played an important role in achieving higher le vels of coverage compared with rural areas where all vaccines are give n by Government agencies, free of charge. In the rural areas, signific antly large variations in coverage were seen among panchayats-large an d peri-urban panchayats had significantly better coverage than small a nd more rural panchayat. Within any given block (the population unit c onsisting of 30-40 panchayats served by a Primary Health Centre), ther e were large variations in the levels of immunization coverage between panchayat. We believe that the variations in coverage levels in urban and rural areas and within rural areas reflect the efficiency of diff erent immunization delivery systems or the staff themselves that serve such regions. Thus, neither the district nor the block is a satisfact ory unit for coverage surveys, unless samples from areas stratified as towns and blocks and within blocks, panchayats stratified by their po pulation size and proximity or distance from towns are selected. For d etecting poorly immunized areas, information from each geographical ar ea served by a health worker should be collected. As the system advanc es, coverage surveys should be replaced with auditing of immunization and also disease surveillance.