AbbreviationsCOVID-19 (coronavirus disease 2019), CT (computed tomography), CXR (chest radiograph), RT-PCR (reverse transcriptase-polymerase chain reaction), ICU (intensive care unit), WBC (white blood cell), LDH (lactate dehydrogenase), CRP (C-reactive protein)
SummaryVaccinated patients with COVID-19 breakthrough infections showed fewer chest CT findings of pneumonia compared to unvaccinated patients.
Key Results1. Of 761 hospitalized patients with COVID-19 disease and chest radiographs, 77% (587/761) were in unvaccinated patients while breakthrough infection in fully vaccinated subjects occurred in 6.2% (47/761) patients.2. The initial chest x-ray showed no pneumonia in 75% of fully vaccinated patients with breakthrough infection and 63% of unvaccinated patients (p=.37).3. In 412 patients with chest CT during hospitalization, a CT showed no pneumonia in 59% of fully vaccinated patients with breakthrough infection and 27% of unvaccinated patients (p=.01).
Background
Few reports have evaluated the effect of the SARS-CoV-2 variant and
vaccination on the clinical and imaging features of COVID-19.
Purpose
To evaluate and compare the effect of vaccination and variant prevalence
on the clinical and imaging features of infections by the
SARS-CoV-2.
Materials and Methods
Consecutive adults hospitalized for confirmed COVID-19 at three centers
(two academic medical centers and one community hospital) and registered
in a nationwide open data repository for COVID-19 between August 2021
and March 2022 were retrospectively included. All patients had available
chest radiographs or CT. Patients were divided into two groups according
to predominant variant type over the study period. Differences between
clinical and imaging features were analyzed using Pearson
χ
2
test, Fisher exact test, or the independent
t-test. Multivariable logistic regression analyses were used to evaluate
the effect of variant predominance and vaccination status on imaging
features of pneumonia and clinical severity.
Results
Of the 2180 patients (mean age, 57 years ± 21, 1171 women), 1022
patients (46%) were treated during the Delta variant predominant period
and 1158 (54%) during the Omicron period. The Omicron variant prevalence
was associated with lower pneumonia severity based on CT scores (OR,
0.71 [95% CI: 0.51, 0.99; P = .04]) and lower clinical severity based on
ICU admission or in-hospital death (OR 0.43, 95% CI: 0.24, 0.77, P =
.004) than the Delta variant prevalence. Vaccination was associated with
the lowest odds of severe pneumonia based on CT scores (OR 0.05, 95%
CI:0.03, 0.13, P < .001) and clinical severity based on ICU
admission or in-hospital death (OR 0.15, 95% CI: 0.07, 0.31, P <
.001) relative to no vaccination.
Conclusion
The SARS-CoV-2 Omicron variant prevalence and vaccination were associated
with better clinical outcomes and lower severe pneumonia risk relative
to Delta variant prevalence.
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