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The COVID-19 hospitalization metric in the pre- and postvaccination eras as a measure of pandemic severity: A retrospective, nationwide cohort study

Published online by Cambridge University Press:  11 January 2022

Nathanael R. Fillmore
Affiliation:
Department of Medicine, Veterans’ Affairs (VA) Boston Healthcare System, Boston, Massachusetts Dana Farber Cancer Institute, Boston, Massachusetts Harvard Medical School, Boston, Massachusetts
Jennifer La
Affiliation:
VA Boston Cooperative Studies Program, Boston, Massachusetts
Chunlei Zheng
Affiliation:
VA Boston Cooperative Studies Program, Boston, Massachusetts
Shira Doron
Affiliation:
Division of Geographic Medicine and Infectious Diseases, Tufts Medical Center, Boston, Massachusetts
Nhan V. Do
Affiliation:
Department of Medicine, Veterans’ Affairs (VA) Boston Healthcare System, Boston, Massachusetts VA Boston Cooperative Studies Program, Boston, Massachusetts Boston University School of Medicine, Boston, Massachusetts
Paul A. Monach
Affiliation:
Department of Medicine, Veterans’ Affairs (VA) Boston Healthcare System, Boston, Massachusetts Harvard Medical School, Boston, Massachusetts VA Boston Cooperative Studies Program, Boston, Massachusetts
Westyn Branch-Elliman*
Affiliation:
Department of Medicine, Veterans’ Affairs (VA) Boston Healthcare System, Boston, Massachusetts Harvard Medical School, Boston, Massachusetts VA Boston Cooperative Studies Program, Boston, Massachusetts VA Boston Center for Healthcare Organization and Implementation Research, Boston, Massachusetts
*
Author for correspondence: Westyn Branch-Elliman, E-mail: Westyn.Branch-Elliman@va.gov

Abstract

Background:

Coronavirus disease 2019 (COVID-19) hospitalization definitions do not include a disease severity assessment. Thus, we sought to identify a simple and objective mechanism for identifying hospitalized severe cases and to measure the impact of vaccination on trends.

Methods:

All admissions to a Veterans’ Affairs (VA) hospital, where routine inpatient screening is recommended, between March 1, 2020, and November 22, 2021, with laboratory-confirmed severe acute respiratory coronavirus virus 2 (SARS-CoV-2) were included. Moderate-to-severe COVID-19 was defined as any oxygen supplementation or any oxygen saturation (SpO2) <94% between 1 day before and 2 weeks after the positive SARS-CoV-2 test. Admissions with moderate-to-severe disease were divided by the total number of admissions, and the proportion of admissions with moderate-to-severe COVID-19 was modelled using a penalized spline in a Poisson regression and stratified by vaccination status. Dexamethasone receipt and its correlation with moderate-to-severe cases was also assessed.

Results:

Among 67,025 admissions with SARS-CoV-2, the proportion with hypoxemia or supplemental oxygen fell from 64% prior to vaccine availability to 56% by November 2021, driven in part by lower rates in vaccinated patients (vaccinated, 52% versus unvaccinated, 58%). The proportion of cases of moderate-to-severe disease identified using SpO2 levels and oxygen supplementation was highly correlated with dexamethasone receipt (correlation coefficient, 0.95), and increased after July 1, 2021, concurrent with δ (delta) variant predominance.

Conclusions:

A simple and objective definition of COVID-19 hospitalizations using SpO2 levels and oxygen supplementation can be used to track pandemic severity. This metric could be used to identify risk factors for severe breakthrough infections, to guide clinical treatment algorithms, and to detect trends in changes in vaccine effectiveness over time and against new variants.

Type
Original Article
Copyright
© The Author(s), 2022. Published by Cambridge University Press on behalf of The Society for Healthcare Epidemiology of America

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Footnotes

a,b

Authors of equal contribution.

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