This study assessed opioid-involved overdose rates by age, sex, and race-ethnicity across strict pandemic mitigation phases and how this varied across data systems.

We examined opioid-involved overdoses using medical examiner and hospital data for Cook County, Illinois between 2016 to 2021. Multivariable segmented regression was used to assess weekly opioid overdose rates across subgroups of age, sex and race/ethnicity and strict pandemic mitigation phases.

The overall rate of weekly opioid-involved overdoses increased when assessing the medical examiner (β=0.01;95%CI=0.01,0.02;p=<0.001) and emergency department visits data sources (β=0.15;95%CI=0.09,0.20;p=<0.001) but not for the hospital admissions data source. We found differences in overdose rates across subgroups and phases of pandemic mandates. Fatal overdoses increased during lockdown-1 while admissions and ED visits for opioid-involved overdoses generally decreased across all phases of pandemic mitigation mandates except for the period following lockdown-1. Across pandemic mitigation phases, Hispanics and individuals under 25 years did not demonstrate any change in admissions and ED visits for overdoses.

We observed an increase in fatal opioid-involved overdose rates and decline in rates for both admissions and ED visits across the pandemic mitigation phases. Our findings underscore the importance of utilizing multiple sources of surveillance to better characterize opioid-involved overdoses and for public health planning.