COPENHAGEN, Denmark — New research warns that the Omicron variant of SARS-CoV-2 is actually deadlier than seasonal flu bugs. Study authors report that hospitalized adult patients with a case of influenza during the 2021-2022 flu season were 55 percent less likely to die over the next month than hospitalized patients testing positive for the COVID-19 Omicron variant.
The observation that adults carrying Omicron variant have a higher death rate than others dealing with a seasonal flu virus is especially notable because Omicron is generally seen as less virulent with lower fatality rates than both the Delta and Alpha strains of SARS-CoV-2.
This latest project, led by Dr. Alaa Atamna and colleagues from the Rabin Medical Center at Belinison Hospital in Israel, reports adults 18 and older with influenza were 55 percent less likely to die over the next 30 days than those with Omicron during the 2021-2022 flu season. Both influenza and COVID-19 are respiratory diseases featuring similar modes of transmission.
In December 2021, influenza re-emerged in Israel after going undetected since March 2020. Meanwhile, the Omicron variant of COVID-19 overtook Delta as the predominant variant at that time. However, data directly comparing Omicron with seasonal influenza was scarce.
In an effort to find out more, researchers compared the clinical outcomes of patients hospitalized with COVID’s Omicron variant with those hospitalized with flu at a large academic hospital in Israel. All in all, the study encompassed both consecutive patients hospitalized with laboratory confirmed COVID-19 (167 patients; average age 71, 58% male) and influenza infection (221 patients; average age 65, 41% male) between December 2021 and January 2022.
A total of 63 patients died within the 30-day time period — 19 (9%) hospitalized for the flu and 44 (26%) hospitalized with Omicron.
Is there an underlying reason Omicron was worse than the flu?
Omicron patients also tended to display higher overall comorbidity scores, needed more assistance performing daily living tasks (e.g., washing and dressing), and were more likely to have high blood pressure and diabetes. On the other hand, asthma was more common among those hospitalized with influenza. Both respiratory complications and need for oxygen support/mechanical ventilation were more common among Omicron patients as well.
“A possible reason for the higher Omicron death rate is that patients admitted with Omicron were older with additional major underlying illnesses such as diabetes and chronic kidney disease,” says Dr. Atamna in a media release. “The difference might also be due to an exaggerated immune response in COVID-19, and that vaccination against COVID-19 was far lower among patients with Omicron.”
“The double whammy of overlapping influenza and COVID-19 epidemics will increase the complexity of disease and the burden on health systems. There is one basic step people can take that may alter the trajectory of either epidemic, get the vaccines for flu and COVID-19, especially if you are older and have underlying illnesses.”
Study authors stress that this project was ultimately observational in nature and thus cannot prove causation. It was also conducted in a single hospital in Israel, meaning the results may not translate to other countries and populations. Researchers also can’t rule out the possibility of other unmeasured factors, such as influenza and COVID-19 vaccination status, potentially influencing the results. For instance, the excess mortality observed for Omicron could be the result of an influenza season that was less severe than usual. Finally, this study consisted of only hospitalized patients, so researchers can’t estimate the proportion of hospitalized patients across the total number of infected patients.
Researchers presented their findings at this year’s European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Copenhagen, Denmark.