Correlation Between Pediatrician Supply and Public Health in Japan as Evidenced by Vaccination Coverage in 2010: Secondary Data Analysis

Background: In industrialized countries, assessment of the causal effect of physician supply on population health has yielded mixed results. Since the scope of child vaccination is an indicator of preventive health service utilization, this study investigates the correlation between vaccination coverage and pediatrician supply as a reflection of overall pediatric health during a time of increasing pediatrician numbers in Japan. Methods: Cross-sectional data were collected from publicly available sources for 2010. Dependent variables were vaccination coverage for measles and diphtheria, pertussis, and tetanus (DPT) by region. The primary predictor of interest was number of pediatricians per 10 000-child population (pediatrician density) at the municipality level. Multivariate logistic regression models were used to estimate associations of interest, conditional on a large range of demographic and infrastructure-related factors as covariates, including non-pediatric physician density, total population, per capita income, occupation, unemployment rate, prevalence of single motherhood, number of hospital beds per capita, length of roads, crime rate, accident rate, and metropolitan area code as urban/rural status. The percentage of the population who completed college-level education or higher in 2010 was included in the model as a proxy for education level. Results: Pediatrician density was positively and significantly associated with vaccination coverage for both vaccine series. On average, each unit of pediatrician density increased odds by 1.012 for measles (95% confidence interval, 1.010-1.015) and 1.019 for DPT (95% confidence interval, 1.016-1.022). Conclusions: Policies increasing pediatrician supply contribute to improved preventive healthcare services utilization, such as immunizations, and presumably improved child health status in Japan.