This user story follows Mia Taylor, a fictional 16-month-old child with medical and social care needs, to illustrate challenges in maintaining complete and accurate immunization records across healthcare systems. The case explores how name changes, transitions between providers, and moves between counties can contribute to fragmented records and gaps in childhood immunization data. It also identifies workflow and data-exchange improvements that can help practices reconcile records, coordinate with health plans and immunization registries, reduce manual work, and improve performance on the Childhood Immunization Status Combo 10 measure. Practices and partners can use this resource to examine current processes and identify opportunities to strengthen data quality, information exchange, and care coordination.