Top 5 Takeaways

1. Omicron Predominance: By late December 2021, the Omicron variant became the predominant strain in the U.S., leading to a surge in COVID-19 cases, ED visits, and hospitalizations.
2. Lower Disease Severity: Despite the high number of cases and hospitalizations, indicators of disease severity such as ICU admissions, length of stay, and death rates were lower during the Omicron period compared to previous peaks.
3. Health Care System Strain: The high volume of hospitalizations during the Omicron period strained local health care systems, emphasizing the need for national emergency preparedness and hospital surge capacity.
4. Importance of Vaccination: Higher vaccination coverage and booster doses during the Omicron period likely contributed to the observed lower disease severity.
5. Continued Vigilance Needed: Despite lower severity, the substantial number of daily deaths underscores the importance of staying up to date with vaccinations and following recommended prevention strategies.

Original Article Author and Citation

Corresponding Author

A. Danielle Iuliano, aiuliano@cdc.gov

Suggested Citation

Iuliano AD, Brunkard JM, Boehmer TK, et al. Trends in Disease Severity and Health Care Utilization During the Early Omicron Variant Period Compared with Previous SARS-CoV-2 High Transmission Periods — United States, December 2020–January 2022. MMWR Morb Mortal Wkly Rep 2022;71:146–152. DOI: http://dx.doi.org/10.15585/mmwr.mm7104e4

Summary

The Omicron variant of SARS-CoV-2 led to the highest reported numbers of COVID-19 cases and hospitalizations in the U.S. by late December 2021. Despite this surge, disease severity indicators such as ICU admissions, length of hospital stay, and death rates were lower compared to previous high transmission periods. The high volume of hospitalizations strained local health care systems, highlighting the need for robust emergency preparedness and hospital surge capacity. Increased vaccination coverage and booster doses likely contributed to the observed lower disease severity.

Methods

Data from three surveillance systems and a large healthcare database were analyzed to assess disease severity and healthcare utilization during three high COVID-19 transmission periods: winter 2020–21, Delta predominance (July–October 2021), and Omicron predominance (December 2021–January 2022). Indicators such as daily cases, ED visits, hospital admissions, and deaths were compared across these periods. Statistical analyses were conducted using Python and Kotlin.

Discussion

The Omicron variant’s emergence led to a significant increase in COVID-19 cases, resulting in the highest number of COVID-19-related ED visits and hospital admissions since the pandemic began. However, disease severity indicators were lower during the Omicron period than in previous high transmission periods, likely due to higher vaccination rates and booster doses. Despite lower severity, the high volume of hospitalizations strained healthcare systems, emphasizing the need for emergency preparedness and adequate staffing. Continued monitoring of severity indicators, especially among different age groups and vaccination statuses, is crucial.

Conclusion

The Omicron variant caused a rapid increase in COVID-19 cases and hospitalizations, straining healthcare systems despite lower disease severity. The findings highlight the importance of maintaining high vaccination coverage and booster doses, as well as robust national emergency preparedness to manage healthcare system demands. Staying up to date with vaccinations and following prevention strategies remain critical to reducing infections, severe illness, and deaths from COVID-19.

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