According to a new Israeli study, adult patients hospitalized with a case of influenza in 2021-2022 were 55% less likely to die in the following month than hospitalized patients who tested positive for the Omicron variant of the Covid-19 virus.
- According to the study, adult patients hospitalized with a case of influenza in 2021-2022 were 55% less likely to die in the following month than hospitalized patients who tested positive for the Omicron variant.
- Omicron patients also tended to have higher overall comorbidity scores, were more likely to have high blood pressure and diabetes, experience respiratory complications, and require oxygen assistance.
- The study authors emphasize that this research is observational and therefore cannot prove causation.
The Omicron variant of SARS-CoV-2, the virus that causes Covid-19, is deadlier than seasonal flu viruses. This is revealed by the results of a new study, presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) taking place in Copenhagen, Denmark, from April 15-18.
Omicron patients were 45% more likely to die than those with the flu
The authors of the study, led by Dr. Alaa Atamna and colleagues at Rabin Medical Center at Belinison Hospital in Israel, report that adult patients 18 years and older, hospitalized with a case of influenza during the 2021-2022 influenza, were 55% less likely to die in the following month than hospitalized patients who tested positive for the Omicron variant.
The fact that adults carrying the Omicron variant have a higher mortality rate than patients infected with a seasonal influenza virus was not obvious at first sight, because Omicron is generally considered to be less virulent with mortality rates inferior to Delta and Alpha strains of SARS-CoV-2.
In December 2021, the flu reappeared in Israel after having gone unnoticed since March 2020. Meanwhile, the Omicron variant has overtaken Delta as the predominant variant. However, data directly comparing Omicron to seasonal influenza were scarce. In order to find out more, the researchers compared the clinical results of patients hospitalized for Covid with the Omicron variant (167 patients; average age 71 years, 58% male) with those hospitalized for influenza (221 patients; age average age 65, 41% male) in a large teaching hospital in Israel between December 2021 and January 2022.
Complications more common in Omicron patients
Omicron patients also tended to have higher overall comorbidity scores, needed more help with daily living tasks (bathing, dressing, etc.), and were more likely to suffer from high blood pressure and diabetes. In contrast, asthma was more common among people hospitalized with influenza. Respiratory complications and the need for oxygen support/mechanical ventilation were also more common in Omicron patients.
“A possible reason for the higher mortality rate of the Omicron variant is that patients admitted with Omicron were older and with other major underlying diseases such as diabetes and chronic kidney disease”explains Dr. Atamna in a communicated. “The difference could also be due to an exaggerated immune response in Covid patients and a much weaker Covid-19 vaccination in Omicron patients”says the researcher.
A study with limitations
The study authors emphasize that this research is observational and therefore cannot prove causation. It was also conducted at a single hospital in Israel, which means the results may not translate to other countries and populations. The researchers also cannot rule out the possibility that other unmeasured factors, such as Covid-19 vaccination status, potentially influence the results.
For example, the excess mortality observed for Omicron could be the result of a less severe flu season than usual. Finally, this study only included hospitalized patients, so the researchers cannot estimate the proportion of hospitalized patients out of the total number of infected patients.
