[Relationship between BCG immunization coverage and the immunization delivery system in the Tama area of Tokyo]

The BCG immunization has long been performed in Japan. Although the BCG immunization service is the responsibility of the municipality, the manner in which the BCG immunization is delivered differs from municipality to municipality. The purpose of this study was to clarify how the different manner of the BCG immunization delivery systems influenced the BCG immunization coverage.

The study of BCG immunization coverage was conducted in the Tama area located in the western suburbs of Tokyo in 2004. The birth data and the immunization history by the age of 3 years were collected in the three-year-old health check-up from a total of 2,341 children residing in the Tama area. Based on the age at immunization for each child, the BCG immunization coverage was calculated according to the types of the BCG immunization delivery system. The immunization types were defined as follows; the BCG immunization given on the occasion of the mass health check-up (Group 1); the exclusive mass BCG immunization in a monthly service (Group 2); the exclusive mass BCG immunization in a bimonthly service (Group 3); the exclusive mass BCG immunization in services of fewer than every two months (Group 4); and the immunization given on an individual basis by a general practitioner (Group 5). A univariate analysis was performed to examine the relationship between the BCG immunization coverage by the age of 6 months and the difference among the BCG immunization delivery systems, followed by a multivariate regression analysis to adjust for the factors related to the demography, health care services and the socio-economic status of the municipalities.

Unadjusted odds ratios and adjusted odds ratios for BCG unimmunized children under the age of 6 months by the BCG immunization delivery manner groups were OR 1 reference, adj. OR 1 reference in Group 1; OR 1.42 CI 0.87-2.29, adj. OR 4.01 CI 2.24-7.11 in Group 2; OR 4.96 CI 3.66-6.82, adj. OR 15.59 CI 10.10-24.49 in Group 3;OR 18.60 CI 13.77-25.49, adj. OR 48.17 CI 29.62-79.75 in Group 4; and OR 4.24 CI 2.86-6.31, adj. OR 15.61 CI 9.05-27.26 in Group 5. The univariate analysis and multivariate regression analysis revealed an influence of the BCG immunization delivery manner on the BCG immunization coverage.

The choice of BCG immunization delivery manner is very important to raise the BCG immunization coverage. The BCG immunization given on the occasion of the mass health check-up and the high-frequent immunization service are thought to improve the BCG immunization coverage.