Fig. 1

Adjusted risk ratios and differences of COVID-19-associated hospitalization by any UHC, stratified by age group. *COVID-19 = coronavirus disease 2019, UHC = underlying health condition, aRR = adjusted risk ratio, aRD = adjusted risk difference, CI = confidence interval. aRRs estimated by log-binomial regression using Huber-White estimates of the standard error; aRDs estimated using a generalized linear model with a Gaussian distribution and identity link function, and using Huber-White estimates of the standard error. Vertical dashed lines represent the null value of 1.0 in the aRR plot, and the null value of 0.0 in the aRD plot. Analysis of variance used to test for interaction by age group (aRR: p-value = 0.2; aRD: p-value < 0.001). *Among patients with a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reverse transcription polymerase chain reaction (RT-PCR) test, University of Washington Medicine healthcare system, 02/29/2020 to 03/13/2021. ^†Age at first positive SARS-CoV-2 RT-PCR test within University of Washington Medicine. ^‡Adjusted for continuous age (years), sex assigned at birth (female/male), race and ethnicity (Hispanic or Latine, non-Hispanic American Indian or Alaska Native, non-Hispanic Asian, non-Hispanic Black, non-Hispanic Native Hawaiian or Pacific Islander, non-Hispanic White, not recorded), and health insurance status (public, private, uninsured, not recorded); total models also adjusted for age group (18–39, 40–64, 65 + years). ^§An indicator variable of COVID-19-associated hospitalization within University of Washington Medicine. ^‖Difference in cumulative incidence per 1,000 SARS-CoV-2-positive persons over the 13-month study period. ^¶Conditions possibly associated with increased risk of severe COVID-19 per the United States Centers for Disease Control and Prevention [19], (all yes/no) based on electronic health record data; see Supplementary Table 1 (in Additional File 1) for list of conditions