February 10, 2021

Risk of Death From COVID-19 Is 3.5 Times Higher Than From Influenza

Adults admitted to hospital with coronavirus disease 2019 (COVID-19) at 7 hospitals in Ontario during the first wave of the pandemic had significantly greater mortality, intensive care unit (ICU) use, invasive mechanical ventilation use, and hospital length of stay than patients admitted with influenza, according to a study published in the Canadian Medical Association Journal.

“We can now say definitively that COVID-19 is much more severe than seasonal influenza,” said Amol Verma, MD, St. Michael’s Hospital, and the University of Toronto, Toronto, Ontario. “Patients admitted to hospital in Ontario with COVID-19 had a 3.5 times greater risk of death, 1.5 times greater use of the ICU, and 1.5 times longer hospital stays than patients admitted with influenza.”

The study compared hospitalisations for influenza between November 1, 2019, and June 30, 2020, in 7 large hospitals in Toronto and Mississauga -- areas with large populations and high levels of COVID-19. It included all patients admitted to medical services or the ICU for influenza or COVID-19. There were 783 hospitalisations for influenza in 763 unique patients compared with 1,027 hospitalisations for COVID-19 in 972 unique patients (representing 23.5% of all hospitalisations for COVID-19 in Ontario during the study period).

Most patients hospitalised with COVID-19 had comorbidities, and 21% were aged younger than 50 years. People aged younger than 50 years also accounted for almost 1 in 4 (24%) admissions to the ICU.

“Many people believe that COVID-19 mainly affects older people,” said Dr. Verma. “It is true that COVID-19 affects older adults most severely. We found that among adults over 75 years who were hospitalised with COVID-19, nearly 40% died in hospital. But it can also cause very serious illness in younger adults. Adults under 50 accounted for 20% of all COVID-19 hospitalisations in the first wave of the pandemic. Nearly 1 in 3 adults younger than 50 hospitalised with COVID-19 required intensive care, and nearly 1 in 10 required an unplanned readmission to hospital after discharge.”

People hospitalised for COVID-19 had greater use of the ICU, were more likely to be put on a ventilator and had longer hospital stays than people with influenza.

“These differences may be magnified by low levels of immunity to the novel coronavirus compared with seasonal influenza, which results from past infections and vaccination,” said Dr. Verma. “Hopefully, the severity of COVID-19 will decrease over time as people are vaccinated against the virus and more effective treatments are identified. There is, unfortunately, also the possibility that variants of the virus could be even more severe.”

Reference: https://www.cmaj.ca/content/cmaj/early/2021/02/10/cmaj.202795.full.pdf

SOURCE: Canadian Medical Association Journal
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