The Effect of Interjurisdictional Data Exchange on Immunization Data in Michigan, Minnesota, and Wisconsin

Context: Immunization information systems (IIS) data can be used to routinely monitor immunization coverage to monitor geographical vaccination coverage. Analyses for smaller geographical areas are more sensitive to data quality errors and resident mobility, which may bias coverage estimates. Improving these estimates also contributes to health equity because certain small populations may face disproportionate health challenges. Objective: To evaluate how data exchange with adjacent jurisdictions affects immunization coverage estimates in Michigan, Minnesota, and Wisconsin. Design: Retrospective cohort study. Setting & Participants: Immunization data for Michigan, Minnesota, and Wisconsin residents from the Michigan Care Improvement Registry, Minnesota Immunization Information Connection, and Wisconsin Immunization Registry, respectively. Main Outcome Measures: Count of out-of-state immunizations; distribution of residents with at least 1 out-of-state immunization; change in routine childhood, adolescent, and adult influenza and COVID-19 immunization coverage estimates. Results: Despite a modest state-wide impact, analysis in all 3 jurisdictions revealed sizeable effects at the county level, especially in immunization coverage estimates along state borders. In Michigan, 0.3% of IIS residents had received at least 1 vaccination in Wisconsin; including these records led to increases in routine childhood coverage estimates as high as 40% in 1 county. This was also true for Minnesota and Wisconsin, with 8.1% and 3.8% of the population having a known out-of-state vaccine, respectively, driving up routine childhood coverage estimates by 60% or more in some counties. Conclusions: IIS-to-IIS data exchange has improved capture of certain populations within Michigan, Minnesota, and Wisconsin. In all 3 jurisdictions, the impact of interjurisdictional data exchange was concentrated in border counties, suggesting that jurisdictions with mobile populations along their borders will gain the most from investing in this infrastructure.