EVALUATION OF IMMUNIZATION COVERAGE BY LOT QUALITY ASSURANCE SAMPLINGCOMPARED WITH 30-CLUSTER SAMPLING IN A PRIMARY HEALTH-CENTER IN INDIA

The immunization coverage of infants, children and women residing in a primary health centre (PHC) area in Rajasthan was evaluated both by l ot quality assurance sampling (LQAS) and by the 30-cluster sampling me thod recommended by WHO's Expanded Programme on Immunization (EPI). Th e LQAS survey was used to classify 27 mutually exclusive subunits of t he population, defined as residents in health subcentre areas, on the basis of acceptable or unacceptable levels of immunization coverage am ong infants and their mothers. The LQAS results from the 27 subcentres were also combined to obtain an overall estimate of coverage for the entire population of the primary health centre, and these results were compared with the EPI cluster survey results. The LQAS survey did not identify any subcentre with a level of immunization among infants hig h enough to be classified as acceptable; only three subcentres were cl assified as having acceptable levels of tetanus toroid (TT) coverage a mong women. The estimated overall coverage in the PHC population from the combined LQAS results showed that a quarter of the infants were im munized appropriately for their ages and that 46% of their mothers had been adequately immunized with TT Although the age groups and the per iods of time during which the children were immunized differed for the LQAS and EPI survey populations, the characteristics of the mothers w ere largely similar, About 57% (95% CI, 46-67) of them were found to b e fully immunized with TT by 30-cluster sampling, compared with 46% (9 5% CI, 41-51) by stratified random sampling. The difference was not st atistically significant. The field work to collect LQAS data took abou t three times longer, and cost 60% more than the EPI survey. The appar ently homogeneous and low level of immunization coverage in the 27 sub centres makes this an impractical situation in which to apply LQAS, an d the results obtained were therefore not particularly useful. However , if LQAS had been applied by local staff in an area with overall high coverage and population subunits with heterogeneous coverage, the met hod would have been less costly and should have produced useful result s.