Omicron BA.5 more deadlier Covid variants, flu: US CDC

New York: Patients hospitalised with Omicron BA.5 are more likely to die than those with other Covid-19 variants or with flu, according to a new study led by the US Centers for Disease Control and Prevention (CDC).

The study, published in the Open Forum Infectious Diseases, looked at the proportion of hospitalised Covid-19 and influenza patients admitted to a US intensive care unit (ICU) in 2021 and 2022.

The findings showed that the percentage of hospitalised Covid-19 patients admitted to the ICU was similar to seasonal influenza but hospitalised Covid-19 patients during the Omicron BA.5 period continued to experience more in-hospital death than adults hospitalised with influenza.

The association with increased in-hospital death was strongest among adults aged 18-49 years; there was no significant difference in deaths between patients with Covid-19 and influenza among older ages.

"The epidemiology of Covid-19 continues to evolve. Our data suggest that from the Delta-predominant period to the Omicron BA.5-predominant period, the severity of patients hospitalised with Covid-19 generally decreased," said Noah Kojima, from the CDC's Influenza Division in Georgia.

The study included 5,777 and 2,363 eligible adults hospitalised for Covid and flu, respectively.

Amid the Delta variant-predominant period (October to December 2021), 1,632 were hospitalised, compared with 1,451 during the Omicron BA.5 period (June to September 2022).

During the 2011-22 respiratory virus season, 2,363 people were hospitalised for flu.

Although there was a decline in the severity of Covid-19 hospitalisation during the study period, overall severity during later Omicron sublineage periods (BA.2 and BA.5) was generally similar.

Continued monitoring of severity trends is warranted as new variants circulate and population-level immunity changes, the team said.

The reduced disease severity amid Omicron BA.5 predominance is likely multifactorial, including increased population-level SARS-CoV-2 immunity from vaccination and previous infection, broader availability of effective drugs, and refined clinical management strategies, they noted.