(061) Assessment of COVID-19 and Mpox Vaccine Data when Supplementing Administrative Claims with Immunization Information System Data

Publication Number: 398

Background: State-based Immunization Information System (IIS) data can be used to supplement COVID-19 and other vaccine exposure information obtained through administrative claims which can be incomplete. Adverse event signal detection efforts can be improved by linking claims to IIS data through an increase in observed vaccinated population. It is unclear how much vaccine capture improved in demographic and other groups when COVID-19 and Mpox vaccine administration data from IIS are linked to a large administrative claims database.

Objectives: To assess the impact of linking IIS data with administrative claims on COVID-19 and Mpox vaccine ascertainment, and the change in patient population characteristics with vaccine administration information.

Methods: We linked claims from the Healthcare Integrated Research Database (HIRD) to state IIS’ to assess the impact of COVID-19 and Mpox vaccine ascertainment. We established IIS linkages for HIRD members from California, Colorado, Indiana, Kentucky, Massachusetts, Nebraska, New Jersey, New York City, Nevada, Texas, Virginia, and Washington. We included all patients with enrollment at any time from 12/2020 to 5/2023. We quantified characteristics of vaccinees originally identified in claims, to those uniquely added by IIS linkages’.

Results: Of the 18.7 million patients from states with IIS linkages, 31.0% had available COVID-19 vaccine administration data before linkage (from claims) and 43.4% after linkage (from claims and/or IIS), representing a 40.2% increase in the exposed population overall; patients with available Mpox vaccine administration data increased 816.9% after IIS linkage albeit from lower numbers (3,312 in claims versus 27,005 in IIS only). For COVID-19 vaccine administrations among those under 65 years old, percent increases across age groups ranged from 18.0% to 51.5%, with the largest increases observed in the 16-17 and 18-25 year old age groups. Percent increases by sex (male versus female), urbanicity-status (urban versus rural), and year (2022 vs. 2021) were largely consistent. When stratified by state, COVID-19 vaccine ascertainment increased the most after IIS linkage for California and Colorado (56.3% and 51.8%, respectively).

Conclusions: We increased the size of the COVID-19 and Mpox vaccine exposed populations capture by supplementing with data from state IIS linkages, and this increased capture from IIS data continued with vaccinations in 2022. The addition of IIS linkages disproportionately increased COVID-19 vaccine capture for teens and young adults, suggesting the incomplete vaccine capture in claims may not be missing completely at random.