Covid-19's Omicron varient causes less severe infections than delta and other variants: CDC study

The omicron variant of COVID-19 may be more transmissible than previous variants, but it is also associated with less severe disease, accounting for fewer deaths, fewer visits to intensive care units, and shorter hospital stays, according to U.S. Centers for Disease Control and Prevention's (CDC) study released Tuesday.

COVID-19 cases have surged nationwide in recent weeks as the 7-day average for new infections hit an all-time high of 789,960 on Jan. 15.

Despite that, omicron was only responsible for 27 hospitalizations per 1,000 cases, compared to 68 per 1,000 during the peak of the 2020-21 winter surge and 78 per 1,000 during the delta surge.

 

"In addition to lower ratios of [emergency department] visits, hospitalizations, and deaths to cases observed during the Omicron period, disease severity indicators were also lower among hospitalized COVID-19 patients, including ICU admission, receipt of [intermittent mandatory ventilation], length of stay, and in-hospital death," the CDC authors wrote.

The CDC noted that the reduced lethality of omicron is likely due in part to increased immunity from vaccines and prior infection, but the "lower virulence" of the new variant is also partly responsible.

Researchers at the LKS Faculty of Medicine at The University of Hong Kong found in a mid-December study that omicron multiples much faster than previous variants in the human bronchus, which may explain its increased transmissibility, but omicron infection "in the lung is significantly lower than the original SARS-CoV-2, which may be an indicator of lower disease severity."

Other countries, including Scotland, England, and South Africa, have also noted the reduced lethality of omicron, according to the CDC.

While omicron may not be as lethal, the sheer number of cases is still threatening hospitals.

"Although patients hospitalized during the Omicron period have shorter stays and less frequent ICU admissions, the high volume of hospitalizations resulting from high transmission rates during a short period can strain local health care systems in the United States, and the average daily number of deaths remains substantial," the CDC authors wrote.