The current Omicron strain of COVID still appears to be more deadly than the flu, according to new research from Israel.
The data, which was presented to the European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) on 15 – 18 April 2023 in Copenhagen, Denmark, showed that adults hospitalised with influenza were 55% less likely to die within 30 days than those hospitalised with Omicron during the 2021-2022 influenza season.
Even though Omicron has replaced Delta as the predominant variant, research directly comparing Omicron with seasonal influenza has remained scarce.
The study, by Dr Alaa Atamna and colleagues from the Rabin Medical Centre, compared the clinical outcomes of patients hospitalised with the Omicron variant and those hospitalised with influenza at Israel’s Belinison Hospital, following the flu’s re-emergence in December 2021.
As most of the world also reported, influenza disappeared in Israel during the initial waves of the pandemic in March 2020.
A total of 167 patients hospitalised with a confirmed case of infection with Omicron and 221 patients hospitalised with the flu, between December 2021 and January 2022, were included in the study.
Overall, 63 patients died within 30 days; 19 (9%) of those admitted with influenza and 44 (26%) who were hospitalised with Omicron.
“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,” Dr Atamna said, noting that the median age of patients with COVID was 71 years, and just 65 years for influenza.
“The difference might also be due to an exaggerated immune response to COVID, and that vaccination against COVID was far lower among patients with Omicron.”
Participants with COVID tended to have higher overall comorbidity scores, needed more assistance performing daily activities such as washing and dressing, and were more likely to have high blood pressure and diabetes – whereas asthma was most common in those hospitalised with influenza.
Respiratory complications and need for oxygen support and mechanical ventilation were also more common in Omicron cases than flu.
“The double whammy of overlapping influenza and COVID epidemics will increase the complexity of disease and the burden on health systems,” Dr Atamna concluded.
“There is one basic step people can take that may alter the trajectory of either epidemic, get the vaccines for flu and COVID, especially if you are older and have underlying illnesses.”
Their work supports recent findings from Switzerland, published 16 February 2023 in JAMA Network Open, which revealed that Swiss adults hospitalized with Omicron infections died at 1.5 times the rate of those diagnosed as having influenza A or B.
Roughly 80% of both groups had underlying medical conditions, but conversely, fewer COVID patients reported respiratory comorbidities than those with flu (13.1% vs 24.6%).