Risk of death 3.5 times higher for COVID-19 than influenza: CMAJ study

A study published Wednesday in the Canadian Medical Association Journal (CMAJ) found the risk of death from COVID-19 was 3.5 times higher than from influenza.

The numbers put a figure on the severity of the novel coronavirus, which experts have been speaking to since the pandemic began.

The study analyzed hospitalized cases of COVID and influenza between November 2019 and June 2020 in seven Toronto-area hospitals, finding that people admitted with COVID-19 were 1.5 times more likely to need intensive care, and stayed in hospitals 1.5 times longer than patients admitted with influenza.

The study used data extracted from hospital computer systems to describe details of patients’ hospitalizations, says Dr. Amol Verma of St. Michael’s Hospital and the University of Toronto.

That data included things like demographics, vital signs, laboratory test results, use of hospital resources like ventilators, and outcomes of their hospital stay — whether they died in hospital, needed intensive care, or were re-admitted.

The findings from the Canadian study were similar to results recently reported in France and the United States, the CMAJ says.

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“We can now say definitively that COVID-19 is much more severe than seasonal influenza,” Verma said in a release.

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The study described hospitalizations in Toronto and Mississauga, Ont. — areas with large populations and high levels of COVID-19 — and included all patients admitted to medical services or the intensive care units (ICU) for influenza or COVID-19.

There were 1,027 hospitalizations for COVID-19 in 972 patients — some re-admissions were included in the study — compared to 783 hospitalizations for influenza in 763 patients.

Those figures represent 23.5 per cent of all hospitalizations for COVID-19 in Ontario during the study period.

Most patients hospitalized with COVID-19 had few other illnesses, and 21 per cent were younger than 50 years of age. People younger than 50 also accounted for 24 per cent of admissions to the ICU, the study found.

While COVID-19 generally affects older adults more severely, Verma says the study highlights that the illness can also have serious impacts on younger people.

The flu hospitalizations included in the study happened mainly from November 2019 to February 2020, Verma says. While COVID hospitalizations from the study occurred mainly from March to June, Verma adds there were some earlier cases in the Toronto area that were also included.

Verma says the figures may be “magnified” by low levels of immunity to the COVID virus, compared to that of the seasonal flu. He adds that COVID vaccines should help decrease severity of the infection over time.

“There is, unfortunately, also the possibility that variants of the virus could be even more severe,” he added.