Study Finds Clinical, Imaging Characteristics of COVID-19 Are Less Severe in Fully Vaccinated Individuals


Being fully vaccinated was associated with a lower risk of requiring supplemental oxygen compared to being unvaccinated, as well as a lower risk of intensive care unit admission.

Both the clinical and imaging characteristics of COVID-19 tend to be milder in patients who have been fully vaccinated compared to those who are partially vaccinated or unvaccinated, according to research published in Radiology.

COVID-19 vaccines are an effective and vital tool for controlling the pandemic, although vaccination is not 100% effective at preventing illness, according to the study. Breakthrough infections are defined as the detection of SARS-CoV-2 ribonucleic acid (RNA) or antigens in a respiratory specimen collected from an individual 14 days or more after receiving all recommended doses of a COVID-19 vaccine, according to the study.

Importantly, breakthrough cases are on the rise due to the transmissibility of the omicron variant. Because of this, the researchers said it is important to know how vaccination impacts not only COVID-19 disease severity, but also clinical data and medical imaging results.

“Although the risk of infection is much lower among vaccinated individuals and vaccination reduces the severity of illness, clinical and imaging data of COVID-19 breakthrough infections have not been reported in detail,” said senior author Yeon Joo Jeong, MD, PhD, in the press release. “The purpose of this study was to document the clinical and imaging features of COVID-19 breakthrough infections and compare them with those of infections in unvaccinated patients.”

The research team analyzed data from adult patients registered in an open data repository for COVID-19 between June and August 2021. Hospitalized patients with baseline chest X-rays were divided into 3 groups, according to their vaccination status. The researchers then evaluated differences between clinical and imaging features as well as associations between clinical factors and outcomes.

Of the 761 hospitalized patients with COVID-19 included in the analysis, the mean age was 47 years, 51% were women, 6.2% were fully vaccinated, 17% were partially vaccinated, and 77% were unvaccinated.

Chest CT scans were performed on 54% of the patients during their hospitalization. Of those, the proportion of CT scans without pneumonia included 22% of unvaccinated patients, 30% of partially vaccinated patients, and 59% of fully vaccinated patients. Based on this, being fully vaccinated was associated with a lower risk of requiring supplemental oxygen compared to being unvaccinated, as well as a lower risk of intensive care unit (ICU) admission.

The researchers also found associations between the risk of severe disease and clinical characteristics, such as older age, history of diabetes, lymphocytopenia, thrombocytopenia, elevate lactate dehydrogenase, and elevated C-reactive protein. Notably, age was also an important predictor of more severe disease in COVID-19 patients, including among those with a breakthrough infection.

These observed differences in clinical characteristics could reflect differences in vaccination priorities based on underlying comorbidities, according to the researchers. During the study period, high-risk groups, such as individuals over 65 years of age, health care workers, and individuals with disabilities, were priority targets for COVID-19 vaccination. Therefore, elderly patients and those with at least 1 comorbidity were more common in the vaccinated group than in the unvaccinated study group.

“Despite these differences, mechanical ventilation and in-hospital death occurred only in the unvaccinated group,” Jeong said in the press release. “Furthermore, after adjusting for baseline clinical characteristics, analysis showed that fully vaccinated patients were at significantly lower risk of requiring supplemental oxygen and of ICU admission than unvaccinated patients.”

Further research into this issue will be necessary as different variants emerge, according to the study authors. However, the researchers said their findings shed light on the clinical efficacy of COVID-19 vaccination in the context of breakthrough infections.


Study Finds COVID-19 Less Severe in Fully Vaccinated. News release. Radiological Society of North America; February 1, 2022. Accessed February 2, 2022.

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