US Study Finds Omicron Severity On Par With Other COVID Variants

6 May, 2022 21:15 IST

A US study found that Omicron may be intrinsically as severe as previous coronavirus variants, contradicting assumptions that the strain was more transmissible, but less severe. The study, which was published as a pre-print on Research Square on May 2, controlled four factors such as demographics, vaccination status, and the Charlson comorbidity index, which predicts the risk of death within a year of hospitalisation for patients with specific comorbid conditions.

The B.1.1.529 (Omicron) variant has previously been identified as being more transmissible, but less severe than other SARS-CoV-2 variants. To put this assumption to test, the researchers linked state-level vaccination data with quality-controlled electronic health records from a large healthcare system in Massachusetts, which included 13 hospitals. 

The team, which included researchers from Massachusetts General Hospital, Minerva University, and Harvard Medical School in the United States, then compared the risks of hospitalisation and mortality in over 1,30,000 Covid-19 patients across the SARS-CoV-2 waves. 

Although the unadjusted rates of hospital admission and mortality appeared to be higher in previous waves than in the Omicron period, the risks of hospitalisation and mortality were nearly identical. 

"After controlling for confounders, we discovered that the risks of hospitalisation and mortality were nearly identical across time periods." According to the study's authors, "our analysis suggests that the intrinsic severity of the Omicron variant may be as severe as previous variants." 
 

The Omicron variant has been reported as more transmissible, but less severe than the previous variants in a number of locations—including, South Africa, Scotland, England, and Canada, says the researchers. However, they claim that understanding the intrinsic severity of Omicron is difficult.

A number of confounding factors affecting Covid-19 severity have changed since the start of the pandemic and may continue to change," the study's authors wrote. 

"Any comparison between SARS-CoV-2 variants that does not adequately adjust and control for important confounders that change over time, such as vaccination status and healthcare utilisation, can mislead both the public and medical experts about the true danger of the variant," they added

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