Mapping routine measles vaccination and factors related to uncompleted vaccination in Japan: An ecological study

Abstract

ObjectiveFew studies in Japan have considered regional differences in immunisation coverage and have geographically examined its distribution. We aimed to identify the municipal-level distribution of immunisation coverage and explore regional characteristics associated with its regional differences through ecological studies.DesignAn ecological study.SettingJapan municipalities.ParticipantsAll 1737 municipalities.Outcome measureThe mean measles-rubella (MR) vaccination rate distribution from 2013 to 2018 was drawn using GIS. We tested the null hypothesis of non-random distribution using spatial autocorrelation analysis (Global Moran’s I). We presented clusters of municipalities with significantly higher and lower vaccination rates by hot spot analysis (Getis-Ord Gi*). Furthermore, we estimated among municipality characteristics, regional ones associated with vaccination rates.ResultsAccording to Global Moran’s I, the MR vaccine coverage distribution was clustered significantly (z = 11.44, p <0.00). Based on the hot spot analysis, the western Japan region tended to have more cold spots with low inoculation rates, small numbers of births and areas with considerable annual variations in vaccination rates. In multiple regression analysis using regional characteristics as independent variables, the 1-year and 6-month check-up rates (Model 2: 95% confidence interval [CI], 0.21-0.36), number of births (0.96-1.54), and standard deviation of the vaccination rate in a target year per municipality (0.17-0.24), were positively associated with the vaccination rate. Contrariwise, average mothers’ age (−1.15 to -0.34), percentage of single-parent households (−0.48 to -0.17), percentage of households with multiple children (−0.12 to -0.04), and moving-in rates (−0.26 to -0.05) were negatively associated with vaccination rate.ConclusionTo eliminate regional differences in immunisation coverage, it is practical to identify areas with low immunisation coverage for a proactive corrective approach. The regional characteristics identified in this study, such as population structure, administrative characteristics, and trends in socioeconomic status in municipalities will make it possible to identify target areas.Strengths and limitations of this studyThe mean measles-rubella (MR) vaccination rate distribution from 2013 to 2018 was drawn using GIS.We tested the null hypothesis of non-random distribution using spatial autocorrelation analysis (Global Moran’s I).We presented clusters of municipalities with significantly higher and lower vaccination rates by hot spot analysis (Getis-Ord Gi*).Furthermore, we estimated among municipality characteristics, regional ones associated with vaccination rates