Health information systems receive data through various methods. These data exchange methods have the potential to influence data quality. We assessed a de-identified 2010 dataset including 757-476 demographic records and 2-634-101 vaccination records from Washington State's Immunization Information System (IIS) to describe timeliness and completeness of IIS data across several data exchange methods: manual entry- HL7- and flat file upload. Overall- manually-entered data and HL7 records were more timely than records imported as flat files. Completeness- though very high overall- was slightly higher for records arriving via flat file. Washington State IIS users- including clinicians and public health- rely on its data to inform patient care and determine population coverage of immunizations. Our results suggest that although data element completeness in systems like Washington's IIS will likely not be immediately or significantly impacted by provider's migration to HL7 connections with IISs- timeliness could be substantially improved when using HL7 connections.