An economic analysis is presented on the factors that affect households demand for childhood immunization. The analysis is mainly based on the National Immunization Survey (NIS) 2003 Public-Use Data File and supplemented with state Medicaid variables and influenza level variables. A logit regression is estimated for the up-to-date immunization status of children. The regression results imply that factors such as age of children, income, mothers age and education, and Medicaid program have a positive influence on households demand for childrens vaccine. In contrast, the number of children and comprehensive care providers in the household are negatively correlated with up-to-date vaccine status. Oaxaca-Blinder decomposition technique is used in the research to indicate: How much of the gap between vaccination status of two groups of different mothers education is due to difference in characteristics and difference in the estimated coefficients. The decomposition results imply that approximately 35% of the education effect on up-to-date vaccine status can be explained by a households immunization preference.