SARS-CoV-2 Variants Infection in Relationship to Imaging-based Pneumonia and Clinical Outcomes

Abstract

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.

Changes in COVID-19 CT Manifestations with Vaccination and the Omicron Variant

“…On the contrary, Crombé et al found no significant difference in vaccine effectiveness against severe CT pneumonia between the Omicron-predominant and Delta-predominant phases. This result is similar to the findings of Lee et al ( 7 ). Furthermore, vaccine effectiveness did not wane in terms of typical CT findings and the severity of COVID-19 pneumonia.…”

“…Therefore, it is important to assess the impact of vaccination and Omicron on CT manifestations separately. To date, one retrospective study ( 7 ) has examined whether vaccination and Omicron were independently associated with less severe disease. In that study, multivariable analysis showed that although Omicron reduced the risk of severe CT pneumonia (odds ratio [OR], 0.7), vaccination provided an even more significant reduction (ORs, 0.11 for full vaccination and 0.05 for booster vaccination).…”

Current and Emerging Knowledge in COVID-19

“…In 2180 hospitalized patients with COVID-19, CT was more likely to be negative for pneumonia during periods of Omicron versus Delta variant prevalence (71% vs 35%, respectively; P < .001), and the Omicron variant had a lower risk of CT pneumonia severity (odds ratio, 0.71; P = .04) and clinical severity (odds ratio, 0.43; P = .004) than the Delta variant ( 67 ) ( Fig 6 ). The proportion of patients with an atypical CT pattern was higher in the Omicron variant group than in the Delta variant group ( 67 , 68 ) ( Table 2 ) ( Fig 6D ).…”

<strong>Attenuation and Degeneration of SARS-CoV-2 Despite of Adaptive Evolution</strong>

“…Infection with the Omicron variant is characterized by upper respiratory symptoms such as rhinorrhea, sore throat, sneezing, and hoarse voice, while the absence of anosmia may reflect reduced tropism toward extra-respiratory tissues [37]. Moreover, the Omicron variant has been found to be less likely to cause severe pneumonia than the Delta variant even after adjustment for vaccination status in a multivariable analysis [38]. In patients infected with the Omicron variant, pneumonia was more strongly associated with old age, male gender, and diabetes than in patients infected with previous variants [39].…”