Characteristics and outcomes of hospital admissions for COVID-19 and influenza in the Toronto area

CMAJ. 2021 Mar 22;193(12):E410-E418. doi: 10.1503/cmaj.202795. Epub 2021 Feb 10.


Background: Patient characteristics, clinical care, resource use and outcomes associated with admission to hospital for coronavirus disease 2019 (COVID-19) in Canada are not well described.

Methods: We described all adults with COVID-19 or influenza discharged from inpatient medical services and medical-surgical intensive care units (ICUs) between Nov. 1, 2019, and June 30, 2020, at 7 hospitals in Toronto and Mississauga, Ontario. We compared patient outcomes using multivariable regression models, controlling for patient sociodemographic factors and comorbidity level. We validated the accuracy of 7 externally developed risk scores to predict mortality among patients with COVID-19.

Results: There were 1027 hospital admissions with COVID-19 (median age 65 yr, 59.1% male) and 783 with influenza (median age 68 yr, 50.8% male). Patients younger than 50 years accounted for 21.2% of all admissions for COVID-19 and 24.0% of ICU admissions. Compared with influenza, patients with COVID-19 had significantly greater in-hospital mortality (unadjusted 19.9% v. 6.1%, adjusted relative risk [RR] 3.46, 95% confidence interval [CI] 2.56-4.68), ICU use (unadjusted 26.4% v. 18.0%, adjusted RR 1.50, 95% CI 1.25-1.80) and hospital length of stay (unadjusted median 8.7 d v. 4.8 d, adjusted rate ratio 1.45, 95% CI 1.25-1.69). Thirty-day readmission was not significantly different (unadjusted 9.3% v. 9.6%, adjusted RR 0.98, 95% CI 0.70-1.39). Three points-based risk scores for predicting in-hospital mortality showed good discrimination (area under the receiver operating characteristic curve [AUC] ranging from 0.72 to 0.81) and calibration.

Interpretation: During the first wave of the pandemic, admission to hospital for COVID-19 was associated with significantly greater mortality, ICU use and hospital length of stay than influenza. Simple risk scores can predict in-hospital mortality in patients with COVID-19 with good accuracy.

Publication types

  • Comparative Study

MeSH terms

  • Age Factors
  • Aged
  • Aged, 80 and over
  • COVID-19 / diagnosis
  • COVID-19 / epidemiology*
  • COVID-19 / therapy
  • Critical Care / statistics & numerical data*
  • Female
  • Hospitalization / statistics & numerical data*
  • Humans
  • Influenza, Human / diagnosis
  • Influenza, Human / epidemiology*
  • Influenza, Human / therapy
  • Male
  • Middle Aged
  • Ontario
  • Outcome Assessment, Health Care
  • Retrospective Studies
  • Risk Factors
  • Socioeconomic Factors
  • Survival Rate