COVID-19 tied to higher risk of death, health problems than flu

Pearl Toh
03 Feb 2021
COVID-19 vs flu: Far more fatal and damaging

While it is tempting to draw lessons from previous influenza pandemic in dealing with the relatively new COVID-19 pandemic, emerging data show just how much deadlier COVID-19 intrinsically is compared with influenza — with higher rates of deaths and complications among hospitalized patients with COVID-19.

Compared with seasonal influenza, COVID-19 patients were almost five times more likely to die (18.5 percent vs 5.3 percent, hazard ratio [HR], 4.97, 95 percent confidence interval [CI], 4.42–5.58). [BMJ 2020;371:m4677]

COVID-19 patients were also four times more likely to require mechanical ventilation and nearly 2.5 times more likely to require intensive care (HR, 4.01, 95 percent CI, 3.53–4.54 and HR, 2.41, 95 percent CI, 2.25–2.59, respectively) than influenza patients.

In addition, length of hospital stay was longer by 3 days (95 percent CI, 2.20–3.80) among COVID-19 patients vs those infected with seasonal influenza. 

Another separate study showed similar findings: hospitalized COVID-19 patients were almost three times more likely to die in-hospital than patients with influenza (16.9 percent vs 5.8 percent; p<0.0001; age-standardized mortality ratio, 2.82). [Lancet Respir Med 2020;doi:10.1016/S2213-2600(20)30527-0]

Similarly, the rates of mechanical ventilation (9.7 percent vs 4.0 percent; p<0.0001) and ICU admissions (16.3 percent vs 10.8 percent; p<0.0001) were significantly higher among COVID-19 vs influenza patients.

Moreover, COVID-19 was associated with a significant excess risk of respiratory complications as well as extrapulmonary complications, including pulmonary embolism, acute respiratory failure, septic shock, or haemorrhagic stroke compared with influenza (p<0.0001 for all, except p=0.0061 for haemorrhagic stroke). 

“Taken together, our findings clearly indicate that COVID-19 is much more serious than seasonal influenza. 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,” said coprincipal investigator Dr Pascale Tubert-Bitter of L'Institut National de la Santé et de la Recherche Médicale (Inserm), Villejuif, France.

“Physical distancing and the use of face masks are obligatory for all of us until we have a vaccine rolled out for major parts of the population. We should know that we can be infected and can spread the virus without having symptoms, and therefore the rules apply to all,” urged Dr Eskild Petersen from University of Aarhus, Denmark, in a linked commentary. [Lancet Respir Med 2020;doi:10.1016/S2213-2600(20)30577-4]

Surprise finding

One big surprise in the first study came from the finding that COVID-19 patients had an increased risk of developing diabetes compared with influenza patients. The adjusted odds ratio (OR) of incident insulin use was 1.86, translating to nine more cases per 100 patients.

“These patients didn’t have diabetes until they got COVID-19,” said principal investigator Dr Ziyad Al-Aly from Washington University School of Medicine, St Louis, Missouri, US.

Additionally, COVID-19 patients were more likely to experience acute kidney injury (OR, 1.52, 95 percent CI, 1.37–1.69) and to initiate renal replacement therapy (OR, 4.11, 95 percent CI, 3.13–5.40) than those hospitalized for influenza.

The risk of severe septic shock was also fourfold higher in COVID-19 patients than those with influenza (OR, 4.04, 95 percent CI, 3.38–4.83).

The researchers found that the risk of death was greatest in those aged ≥75 years who also had chronic kidney disease or dementia for COVID-19 vs influenza. 

These findings that comorbidities present a risk factor for worse outcome in COVID-19 vs influenza were echoed by the French cohort study by Tubert-Bitter and team. They showed that being obese or overweight, diabetes, hypertension, and dyslipidaemia were more prevalent in COVID-19 patients than those with influenza.  
“[The study] has important messages for the upcoming COVID-19 vaccination. Clearly people with obesity, diabetes, and hypertension must be considered high-risk groups,” pointed out Petersen.

“A deeper understanding of the health risks of COVID-19 helps to anticipate demand for healthcare services and to project mortality with greater accuracy,” explained Al-Aly.

A destructive virus

As COVID-19 is relatively new compared with influenza, Al-Aly believed these findings are just the tip of the COVID-19 iceberg — there could be more complications down the road that has not been considered. 

“It’s a destructive virus ... Already, we’re aware of the long-haulers, or people who get COVID-19 but never fully recover,” he continued.

“Even for people who are fortunate to survive the acute COVID-19 illness, they may be forever scarred by the lasting impact of its long-term clinical complications. The more we understand, the better we can benchmark health-care resources and treat patients,” Al-Aly said.


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