Am J Clin Microbiol Antimicrob | Volume 6, Issue 1 | Case Series | Open Access

Clinical Features of Adult, Hospitalized, Non-Vaccinated COVID-19 Patients during the Omicron Variant Surge

Seki M1,2*, Kondo N2, Hashimoto K2, Ohya Y2, Kotajima F2 and Mitsutake K1,2

1Division of Infectious Diseases and Infection Control, International Medical Center, Saitama Medical University, Japan 2COVID-19 Management Team, International Medical Center, Saitama Medical University, Japan

*Correspondance to: Masafumi Seki 

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Background: The mortality of SARS-CoV-2 infection in non-vaccinated patients is still thought to be high despite the appearance of the omicron subvariant. A total of 36 adult, non-vaccinated patients who were hospitalized with SARS-CoV-2 infection during the omicron variant surge were included in this study. Case Series: Severity of illness at admission was mild, moderate, and severe in 0 (0%), 29 (80.6%), and 7 (19.4%) patients, respectively, and three (3/36=9.1%) patients died. The patients who died were as follows. (Case 1) A 64-year-old man on hemodialysis developed severe pneumonia caused by SARS-CoV-2 infection. His pneumonia did not worsen, but he developed septic shock on day 5 with a catheter-related blood stream infection due to Methicillin-Resistant Staphylococcus aureus (MRSA) and Extended Spectrum Beta-Lactamase (ESBL)-producing Escherichia coli. (Case 2) An 87-year-old man with a history of esophageal cancer had moderate pneumonia at admission, but suddenly developed massive brain hemorrhage on day 6. (Case 3) A 94-year-old man with a history of brain infarction and atrial fibrillation had moderate pneumonia on admission. His pneumonia was improving, but he died on day 7 of acute renal failure and suspected recurrent brain infarction. Conclusion: These data and cases suggest that non-vaccinated patients showed high mortality, especially elderly male patients with underlying diseases. They died due to reasons other than respiratory failure and/or pneumonia, and impairment of blood vessels, especially in the brain, heart, and kidneys, by SARS-CoV-2 infection was thought to have occurred, though the omicron variant has generally low pathogenicity.


SARS-CoV-2; Catheter-related blood stream infection; Hemodialysis; Brain hemorrhage; Acute renal failure; Vaccine


Seki M, Kondo N, Hashimoto K, Ohya Y, Kotajima F, Mitsutake K. Clinical Features of Adult, Hospitalized, Non- Vaccinated COVID-19 Patients during the Omicron Variant Surge. Am J Clin Microbiol Antimicrob. 2023; 6(1): 1064..

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