Kaiser Permanente Southern California compared clinical-outcome data for patients infected with the Omicron and Delta variants of SARS-CoV-2, finding that Omicron cases were associated a reduced risk of severe outcomes, including hospitalization.
Researchers described the data in a study posted on Medrxiv.
The study included 52,297 cases with Omicron and 16,982 cases with Delta in which specimens were tested between November 30, 2021, to January 1, 2022.
Hospital admissions occurred among 235 (0.5%) cases of Omicron and 222 (1.3%) cases of Delta.
Among patients with Omicron variant infections, seven were admitted to intensive care, none received mechanical ventilation and one died. Meanwhile, among patients infected with the Delta variant, 23 were admitted to the ICU, 11 received mechanical ventilation, and 14 died.
The median duration of a hospital stay was 3.4 days shorter for Omicron cases, as compared to patients hospitalized with Delta. This was a 69.6% reduction in hospital length of stay.
The researchers found that the Omicron variant infections were associated with a 52% reduction in hospitalization, 53% reduction in symptomatic hospitalization, 74% reduction in ICU admission, and 91% reduction in mortality.
Commenting on the study, Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky, MD, MPH, said, “The data in this study remained consistent with what we are seeing from Omicron in other countries, including South Africa and the UK, and provide some understanding of what we can expect over the coming weeks as cases are predicted to peak in this country.”
However, Walensky, who was speaking at a news conference of the White House COVID-19 Response Team, said, “While we are seeing early evidence that Omicron is less severe than Delta and that those infected are less likely to require hospitalization, it’s important to note that Omicron continues to be much more transmissible than Delta.”
