 We will perform stratified analyses and multivariate logistic regression modeling to examine whether certain subgroups were more likely initiate and complete the series e.g, vaccine uptake might vary by characteristics such as preferred language, raceethnicity, patient age, or parent educational status. We will use similar methods to also examine our data for confounding, for example, if initiation differs by clinic site. If no interactions are found e.g., outcome estimates are similar for different subgroups, we will report summary chi-square tests that only adjust for potential confounders. 