Objective Recently, in Japan, the compulsory vaccinations administered during early childhood have been becoming increasingly varied. As a result, the vaccination schedule has become complicated. In this study, we aimed to identify the association of time-appropriate vaccination during early childhood (dependent variable) with individual-level factors including socioeconomic status and having a family doctor. We also studied the association of time-appropriate vaccination with community-level factors including the number of pediatricians in a community.Methods Multilevel logistic regression models were used for analysis. Time-appropriate BCG, DPT, and measles vaccinations were the dependent variables. Individual-level data were obtained through a survey of parents of 18-month-old children as part of the final evaluation of "Healthy Parents and Children 21"; community-level data were obtained through a survey of municipalities as part of the aforementioned final evaluation as well as through a national survey. There were 23,583 parents in 430 municipalities who were eligible for analysis.Results Time-appropriate vaccination of infants was carried out by 88.3% of parents. The results of the multilevel logistic regression showed that time-appropriate vaccination was significantly lower for those who did not have a family doctor (adjusted odds ratio [AOR], 0.45; 95% confidence interval [CI], 0.36-0.55), the fourth or later birth order (0.23; 0.19-0.28), mothers aged less than 19 years at childbirth (0.17; 0.13-0.24), full-time working mothers (0.52; 0.47-0.58), and those under very difficult economic conditions (0.66; 0.57-0.77). Among community-level factors, only use of vaccination data by a municipality had a significantly negative association with the dependent variable.Conclusion Not having a family doctor, the mother's young age, late birth order, poor economic status, and full-time working mothers were risk factors associated with delayed vaccinations. It is necessary to improve environments that promote infants having a family doctor as well as to promote special approaches toward families at risk for delayed vaccinations.
Keywords: Healthy Parents and Children 21; density of pediatricians; infant; primary care doctor; time-appropriate; vaccination.