The clinical and imaging features of emerging COVID-19 infections in fully vaccinated patients tend to be milder than those in partially vaccinated or unvaccinated patients, according to a new multicenter study published in the journal Radiology .
The number of confirmed COVID-19 cases worldwide now exceeds 270 million with an overall mortality rate of approximately 2%.
COVID-19 vaccines are effective and critical tools to control the pandemic. However, vaccines are not 100% effective in preventing disease. Emerging infections are defined as the detection of ribonucleic acid (RNA) or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen in a respiratory sample collected from a person 14 days or more after receiving all recommended doses of vaccines against COVID-19.
Breakthrough cases are on the rise with the highly transmissible Omicron variant. Therefore, it is important to know how vaccination affects not only the severity of COVID-19 disease, but also clinical data and medical imaging results.
“Although the risk of infection is much lower among vaccinated people, and vaccination reduces disease severity, clinical and imaging data of emerging COVID-19 infections have not been reported in detail,” said the lead author. of the study, Yeon Joo Jeong, MD. , Ph.D., from the Department of Radiology and Biomedical Research Institute at Pusan National University Hospital in Busan, South Korea. “The purpose of this study was to document the clinical and imaging characteristics of emerging COVID-19 infections and compare them with those of infections in unvaccinated patients.”
In this multicenter retrospective cohort study, Dr. Jeong and colleagues analyzed data from adult patients registered in an open data repository for COVID-19 (Korean Imaging Cohort for COVID-19 (KICC-19)) between June and August. of 2021.
Hospitalized patients with baseline chest radiographs were divided into three groups, according to their vaccination status. The researchers evaluated differences between clinical and imaging characteristics and analyzed associations between clinical factors, including vaccination status, and clinical outcomes.
Of the 761 patients hospitalized with COVID-19, the median age was 47 years and 385 (51%) were women. Forty-seven patients (6.2%) were fully vaccinated (breakthrough infection), 127 were partially vaccinated (17%), and 587 (77%) were unvaccinated.
Chest CT scans were performed in 412 (54%) of the patients during hospitalization. Of patients who underwent CT, the proportion of CT without pneumonia was 22% (71/326) of unvaccinated patients, 30% (19/64) of partially vaccinated patients, and 59% (13/64) of partially vaccinated patients. 22) of fully vaccinated patients.
Fully vaccinated status was associated with a lower risk of requiring supplemental oxygen than unvaccinated status, as well as a lower risk of intensive care unit (ICU) admission.
The results also showed associations between the risk of severe disease and clinical characteristics such as older age, history of diabetes, lymphocytopenia, thrombocytopenia, elevated LDH (lactate dehydrogenase), and elevated CRP (C-reactive protein). Notably, age was also found to be a significant predictor of more severe disease in COVID-19 patients, even in those with advanced infection.
Representative cases showing the extent and patterns of pneumonia on chest x-ray (CXR) and CT images. (A and B) A 65-year-old woman with advanced infection 2 months after a second dose of the Pfizer vaccine (fully vaccinated). The patient had a history of hypertension. (A) Chest X-ray obtained on admission showing no abnormal opacification in both lung areas. The extent of CXR pneumonia was scored as 0 (no evidence of pneumonia). (B) Axial CT image of the chest at the level of the lower lobe (obtained on the same day) showing negative for pneumonia; The extent of pneumonia by CT was scored as 0 (no evidence of pneumonia). (C and D) 48-year-old male 1 month after a first dose of the AstraZeneca vaccine (partially vaccinated). The patient had no history of comorbidity. (C) Chest X-ray obtained on admission showing no abnormal opacification in both lung areas. The extent of CXR pneumonia was scored as 0 (no evidence of pneumonia). (D) Axial chest CT image obtained on the same day shows a unilateral ground-glass opacity with a non-rounded morphology in the left lower lobe (arrows). The extent of pneumonia by CT was graded as 1 (1-25% involvement) and this case was classified as undetermined onset of COVID-19 according to the RSNA chest CT classification system.
The researchers noted that the observed differences in clinical characteristics may reflect differences in vaccination priorities based on underlying comorbidities. During the study period, high-risk groups, such as people over 65 years of age, healthcare workers, and people with disabilities, were priority targets for COVID-19 vaccination. Therefore, elderly patients and patients with at least one comorbidity were more common in the vaccinated group than in the unvaccinated group of the study.
“Despite these differences, mechanical ventilation and death in hospital occurred only in the unvaccinated group,” Dr. Jeong said. “In addition, after adjusting for baseline clinical characteristics, the analysis showed that fully vaccinated patients had a significantly lower risk of requiring supplemental oxygen and ICU admission than unvaccinated patients.”
Although additional research will be needed as different variants emerge, this study sheds light on the clinical effectiveness of COVID-19 vaccination in the context of emerging infections.
