Below is a page from the AHRQ website that explains health information exchange (HIE). About three years ago, I participated in my hospital's selection of an electronic medical/health record vendor. Our parent company provided funds for the health department to be able to access specific data elements in the new system's data warehouse.
Although the health department's representative was a technology buff, it was clear that his colleagues were confused about HIE. Since this group describes itself as a "101" group, I assume backgrounders are ok to post. Please note that the description is slanted in the direction of medical/hospital care. This is not relevant to most public health departments, but the reader can get a good sense of the concept and the importance of clearly defining the data elements to make the effort and cost worthwhile.