Top 5 Takeaways

  1. Significant Decrease in Mortality: In-hospital mortality for COVID-19 patients decreased from 15.1% during the Delta variant period to 4.9% in the later Omicron period (April–June 2022).
  2. High-Risk Groups Predominant: The majority of deaths (81.9%) during the later Omicron period occurred in adults aged ≥65 years, and 73.4% in those with three or more underlying medical conditions.
  3. Vaccination and Early Treatment Critical: Vaccination, early treatment, and nonpharmaceutical interventions are vital for preventing COVID-19 deaths, especially in high-risk individuals.
  4. Reduced Mortality Across All Groups: Decreased in-hospital mortality was observed in all demographic groups during the Omicron period compared to the Delta period.
  5. Factors Contributing to Improved Outcomes: Higher immunity levels from vaccinations and prior infections, early treatments, and lower pathogenicity of Omicron subvariants likely led to improved outcomes.

Original Article Author and Citation

Corresponding Author

Tegan K. Boehmer,

Suggested Citation

Adjei S, Hong K, Molinari NM, et al. Mortality Risk Among Patients Hospitalized Primarily for COVID-19 During the Omicron and Delta Variant Pandemic Periods — United States, April 2020–June 2022. MMWR Morb Mortal Wkly Rep 2022;71:1182–1189. DOI:


The study analyzed in-hospital mortality risk among COVID-19 patients during the Delta and Omicron periods. It found a significant decrease in mortality from 15.1% in the Delta period to 4.9% in the later Omicron period. This decline was evident across various demographic groups, including different ages, genders, races, ethnicities, disability statuses, and numbers of underlying medical conditions.


Data was sourced from the Premier Healthcare Database Special COVID-19 Release, covering 678 hospitals. COVID-19 hospitalizations were identified using ICD-10-CM codes, with mortality risk evaluated across different demographic and clinical characteristics. The analysis included model-estimated adjusted mortality risk differences and ratios.


The reduction in mortality is attributed to factors like higher vaccination and immunity levels, advances in early treatment, and the lower pathogenicity of Omicron subvariants. A larger proportion of hospitalizations and deaths occurred in high-risk groups, indicating a shift in the hospitalized patient profile.


The study concludes that despite the lower mortality rates in the later Omicron period, vaccination, early treatment, and appropriate nonpharmaceutical interventions remain crucial, particularly for high-risk populations. It underscores the need for continuous monitoring of COVID-19–related hospitalizations and mortality to inform public health strategies.

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