While the highly transmissible omicron variant has pushed U.S. cases and hospitalizations to record highs, a smaller proportion of cases resulted in hospitalization compared to earlier pandemic surges, according to the CDC's Jan. 25 Morbidity and Mortality Weekly Report.
To conduct the study, researchers used data from three surveillance systems and a large healthcare database to assess disease severity indicators from Dec. 1, 2020, to Jan. 15, 2022, which covered three separate surge periods, including last summer and fall when delta was predominant.
Findings showed the ratio of peak hospital admissions to cases was 27 hospitalizations per 1,000 cases during the omicron period, lower than the ratios in winter 2020-21 and during delta's predominance at 68 per 1,000 and 78 per 1,000, respectively.
The ratios of emergency department visits to cases and deaths to cases were also lower during the omicron period. When looking at hospitalized COVID-19 patients from 199 hospitals during the omicron wave, the mean length of stay and percentages of those who were admitted to an intensive care unit, required ventilation, or died while in the hospital were lower than earlier surges.
The report linked the apparent lower disease severity from omicron to higher vaccination coverage and infection-acquired immunity, as well as lower virulence of the variant.
Despite the observed lower disease severity indicators with omicron, "the high volume of ED visits and hospitalizations can strain local healthcare systems in the U.S., and the average daily number of deaths remains substantial," the CDC said.
The daily average for hospital admissions reached its highest during the omicron surge, according to the report. Meanwhile, the seven-day average for new daily COVID-19 deaths reached 2,188 on Jan. 24, the highest levels since early 2021. To read more about current omicron forecasts, click here.
To view the full CDC report, click here.