Limitations of immunization registers at community health centers for measuring immunization coverage: a case study of the Japanese encephalitis mass immunization program in Bali Province, Indonesia

OBJECTIVES: The aim of this study was to compare the coverage of Japanese encephalitis (JE) immunization obtained from a recall survey and immunization registers at community health centers (CHCs) in Bali Province, Indonesia. METHODS: A population-based survey was conducted, and random 2-staged selection of clusters of sub-villages was performed. The sample consisted of households with children aged 9 months to 15 years old. Interviews were carried out with carers to recall JE immunization status. The recall immunization status was considered valid when name, date, and confirmation of immunization were available in an immunization register at a CHC. Descriptive analysis was performed. The completeness of the information within immunization registers at CHCs was assessed. RESULTS: The coverage of JE immunization obtained from the recall survey was 93.8% (95% confidence interval [CI], 92.8–94.9). It decreased to 74.9% (95% CI, 72.8–77.2) after being validated against immunization registers. The recall coverage of JE immunization was significantly higher than immunization register data suggested. This discrepancy varied from 6.5% to 36.4% across 6 districts; however, none of these districts achieved the recommended target coverage of 95%. The quality of immunization registers varied across CHCs. CONCLUSION: The use of an immunization register may result in underestimating the true coverage of vaccination programs, and its utilization for measuring immunization coverage requires further consideration.