TORONTO -- There is mounting evidence to show that COVID-19 causes more serious outcomes than seasonal influenza, resulting in a much higher death rate among hospitalized patients.
A newly published study based on French national data comparing patients admitted to hospital with COVID-19 to those admitted with seasonal influenza shows a greater proportion of COVID-19 patients experience severe illness requiring intensive care, with a death rate nearly three times higher.
The study compared data from 89,530 patients hospitalized with COVID-19 between March and April with data from 45,819 patients hospitalized with seasonal influenza between December 2018 and February 2019.
According to the data, 16.3 per cent of COVID-19 patients were admitted to intensive care, compared to 10.8 per cent of flu patients. The average stay in the ICU with COVID-19 was nearly twice as long at 15 days, versus eight days for those with the flu.
COVID-19 patients were also twice as likely as flu patients to require mechanical ventilation during their hospital stay. More than one in four COVID-19 patients experienced acute respiratory failure, where the lungs are unable to get enough oxygen into the body, compared with less than one in five patients with the flu.
Nearly twice as many people were admitted to hospital for COVID-19 at the height of the pandemic in France than were for influenza at the peak of the 2018/2019 flu season.
Study authors note that the difference in hospitalization rate may be due in part to existing immunity to influenza in the population thanks to a previous infection or vaccination. Because COVID-19 is a new virus, immunity levels are presumed to be low.
But researchers say their findings reinforce the importance of preventing the spread of both diseases as countries around the world grapple with a second wave of COVID-19 infections overlapping with the onset of seasonal influenza.
“Our study is the largest to date to compare the two diseases and confirms that COVID-19 is far more serious than the flu,” study lead Catherine Quantin, from the University hospital of Dijon and from L'Institut National de la Santé et de la Recherche Medicale (Inserm), said in a press release.
“The finding that the COVID-19 death rate was three times higher than for seasonal influenza is particularly striking when reminded that the 2018/2019 flu season had been the worst in the past five years in France in terms of number of deaths.”
The study also looked at the rate of children hospitalized with both viruses. Fewer children under 18 years old were hospitalized with COVID-19, compared to the flu. However, among those aged five years and under, a larger proportion of COVID-19 patients required intensive care support than those with influenza.
But the study, funded by the French National Research Agency, does mention several limitations.
Most notably, testing practices for the flu were likely variable across hospitals, whereas testing for COVID-19 would have been more common due to the pandemic. According to the authors, this may account for the increased numbers of patients admitted to hospital with COVID-19 compared with seasonal influenza.
Still, the authors say the largest-of-its-kind study shows how important it is to curb the spread of the novel coronavirus.
“Taken together, our findings clearly indicate that COVID-19 is much more serious than seasonal influenza,” study author Dr. Pascale Tubert-Bitter said in a press release.
“At a time when no treatment has been shown to be effective at preventing severe disease in COVID-19 patients, this study highlights the importance of all measures of physical prevention and underlines the importance of effective vaccines.”