• Chan Mi Lee, Eunyoung Lee, Wan Beom Park, Pyoeng Gyun Choe, Kyoung-Ho Song, Eu Suk Kim, and Sang-Won Park.
• Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
• J. Korean Med. Sci. 2022 Aug 15; 37 (32): e252.

BackgroundThe clinical features of coronavirus disease 2019 (COVID-19) patients in the COVID-19 vaccination era need to be clarified because breakthrough infection after vaccination is not uncommon.MethodsWe retrospectively analyzed hospitalized COVID-19 patients during a delta variant-dominant period 6 months after the national COVID-19 vaccination rollout. The clinical characteristics and risk factors for severe progression were assessed and subclassified according to vaccination status.ResultsA total of 438 COVID-19 patients were included; the numbers of patients in the unvaccinated, partially vaccinated and fully vaccinated groups were 188 (42.9%), 117 (26.7%) and 133 (30.4%), respectively. The vaccinated group was older, less symptomatic and had a higher Charlson comorbidity index at presentation. The proportions of patients who experienced severe progression in the unvaccinated and fully vaccinated groups were 20.3% (31/153) and 10.8% (13/120), respectively. Older age, diabetes mellitus, solid cancer, elevated levels of lactate dehydrogenase and chest X-ray abnormalities were associated with severe progression, and the vaccination at least once was the only protective factor for severe progression. Chest X-ray abnormalities at presentation were the only predictor for severe progression among fully vaccinated patients.ConclusionIn the hospitalized setting, vaccinated and unvaccinated COVID-19 patients showed different clinical features and risk of oxygen demand despite a relatively high proportion of patients in the two groups. Vaccination needs to be assessed as an initial checkpoint, and chest X-ray may be helpful for predicting severe progression in vaccinated patients.© 2022 The Korean Academy of Medical Sciences.

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