Linked Immunization Information System, Claims Data Captured COVID-19 Vaccination Status Better Than Claims Data Alone


Reporting vaccination data to Immunization Information Systems databases can support public health surveillance activities.

Integrating Immunization Information Systems (IIS) vaccination records into claims data (collected by health insurers) increased the number of people identified as being vaccinated against COVID-19, according to the results of a study published in JAMA Network Open. Having accurate COVID-19 vaccination data is important for future COVID-19 vaccine studies that capture efficacy and safety, according to the study.

Credit: Jacob Lund -

Credit: Jacob Lund -

When claims data were supplemented with IIS vaccination records, the proportion of participants with at least 1 vaccine dose rose from 32.8% to 48.1%. And when IIS vaccine records were included with claims data, the percentage of people who completed a vaccine series increased from 24.4% to 41.9%, varying by state.

IIS databases are centralized, population-based computerized systems that contain vaccine records. They provide information about all doses administered by a participating vaccine provider, even if the provider did not submit a billing claim. Health insurance claims also capture vaccine administrations, but not completely.

The current study was conducted by the FDA’s Center for Biologics Evaluation and Research (CBER). Investigators aimed to understand how linking ISS data to claims data could improve the COVID-19 vaccine data collected by health insurance claims for a commercially insured population. Investigators also estimated the extent to which linked IIS and claims data misclassified vaccinated individuals as being unvaccinated.

Primary outcomes include the estimated proportion of individuals with at least 1 dose of any COVID-19 vaccine and proportion of individuals with a complete vaccine series (according to general population guideline). Analyzing data of 5,112,722 individuals, investigators identified that a linked ISS and claims databased improved estimates of the proportion of individuals who received a COVID-19 vaccine. However, compared to CDC data, state Department of Health (DOH) data, and capture-recapture analysis, the linked database had more misclassified estimates.

State-specific vaccination estimates from linked IIS records and claims data were 12.1% to 47.1% lower than age-standardized estimates from the Centers for Disease Control and Prevention (CDC). In addition, the linked data provided 9.1% to 46.9% lower vaccination estimates than state DOH, and it possibly provided a 50% lower estimate of vaccination status than capture-recapture analysis.

The study includes some limitations, including the underestimation of the number of individuals who completed a vaccine series. There may be differences in the matching quality of IIS data and claims, and results are only applicable to COVID-19 coverage for commercially insured people in a limited number of US states.

Reporting vaccination data to IIS databases and data exchanges would allow for consistent updates of vaccine status for all US individuals and vaccines to improve public health. The findings highlight the importance of using a variety of data sources, accounting for health coverage gaps, and “highlighted the difficulty of estimating vaccination coverage without a universal health identifier,” the study authors wrote in the article.


Schneider K, Bell E, Zhou C, et al. Use of Immunization Information Systems in Ascertainment of COVID-19 Vaccinations for Claims-Based Vaccine Safety and Effectiveness Studies.

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