OBJECTIVES: We reported two peaks in in-hospital mortality by February 2021 after the initial decline from April through June 2020 among hospitalized patients with coronavirus disease 2019 (COVID-19) in a previous study. This study aimed to assess potential changes in in-hospital mortality among COVID-19 inpatients in the United States from February to October 2021 when vaccination became more common and two significant variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) swiped the nation.

METHODS: A retrospective cross-sectional study was performed for hospitalized adult patients discharged from 816 geographically diverse US hospitals included in the Premier Healthcare Database (PHD) with a principal or secondary discharge diagnosis of COVID-19 between February 1, 2021−October 31, 2021. We assessed both crude and adjusted monthly trends of in-hospital mortality.

RESULTS: Among 341,757 COVID-19 inpatients, the average age was 59 years, 50.7% were men, 58.5% were white, 17.2% were black, and 15.6% were Hispanic. Although in-hospital mortality was high in February (13.7%), it remained below 10% in all months between March and July of 2021. The lowest level of in-hospital mortality was observed in July 2021 (8.0%), which was lower than the lowest level in 2020 (~10%). However, in-hospital mortality sharply increased in August through October (11.3% to 14.9%) when the SARS-CoV-2 delta variant became more prevalent. Trends of in-hospital mortality remained similar after adjusting for differences in patient and hospital characteristics.

CONCLUSION: Although the in-hospital mortality among COVID-19 inpatients decreased from February to July 2021, with the widespread of SARS-CoV-2 delta variant, the in-hospital mortality increased significantly from August to October and surpassed the earlier peak in February of 2021. COVID-19 remains deadly among hospitalized patients and poses significant burden on hospitals.