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Background rates of medical events of interest before and during the COVID-19 pandemic: a longitudinal cohort study using claims data

Health

Importance Background rates are critical for contextualising safety signals arising from COVID-19-related interventions in investigational or real-world settings. Objective To estimate background rates of medical events of interest (MEI) for which COVID-19 infection and/or COVID-19 interventions may be risk factors in two US claims databases. Design, setting and participants This retrospective cohort study spans the pre-COVID-19 (2018–2019) and COVID-19 (2020–2021) periods. We constructed three cohorts, in each of Inovalon/HealthVerity (Inovalon/HV) and Optum databases: a COVID-19-positive adult cohort (2020–2021), a paediatric cohort (2018–2021) and a high-risk cohort (2018–2021) comprising patients at increased risk for severe COVID-19. Participants were indexed on the day they first qualified to enter each cohort during the study period.

BMJ     Jun 27, 2025