Abstract
Public health agencies established immunization registries - now called Immunization Information Systems (IIS) - to consolidate records across provider locations to support more effective immunization of patients and public health surveillance. While initially collecting data through interactive client-server and then web-based interfaces, IIS now collect the vast majority of their data through automated interfaces to electronic health record (EHR) systems using standard application programming interfaces (API). IIS have sophisticated processing rules for the incoming data to ensure data accuracy and completeness. This paper will review the existing workflow, standards, and processes used by IIS to accept, process, and make immunization data available. This will include a review of emerging standards - Fast Healthcare Interoperability Resources (FHIR) - which will likely become dominant over the next few years.