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A Comparison of Clinical Presentations in Coronavirus Disease 2019 Caused by Different Omicron Variants in Japan: A

Ryutaro Hirama1, Kenichiro Takeda1, Seiichiro Sakao1

  • 1Department of Respirology, Graduate School of Medicine, Chiba University, Japan.

Internal Medicine (Tokyo, Japan)
|May 24, 2023
PubMed

Insights

The seventh wave of Omicron BA.5 COVID-19 showed less pneumonia risk than the sixth wave (BA.1/BA.2). However, COVID-19 patients with underlying conditions still face mortality risks from disease exacerbation.

Area of Science:

  • Infectious Diseases
  • Virology
  • Clinical Medicine

Background:

  • The COVID-19 pandemic has been characterized by the emergence of new SARS-CoV-2 variants.
  • Omicron subvariants BA.1/BA.2 and BA.5 dominated distinct waves, necessitating an understanding of their clinical impact.

Purpose of the Study:

  • To compare clinical differences in coronavirus disease 2019 (COVID-19) patients between the Omicron BA.1/BA.2 dominant sixth wave and the Omicron BA.5 dominant seventh wave.
  • To assess variations in clinical presentation, prognosis, and nosocomial infections.

Main Methods:

  • Retrospective, single-center, observational study.
  • Inclusion of 190 COVID-19 inpatients from the sixth (n=93) and seventh (n=97) waves.
  • Comparative analysis of clinical features, outcomes, and infection rates.

Main Results:

  • No significant difference in overall COVID-19 severity was observed between waves.
  • Higher incidence and severity of COVID-19-induced pneumonia in the sixth wave (BA.1/BA.2) compared to the seventh wave (BA.5).
  • Increased rates of nosocomial infections were noted in the seventh wave.

Conclusions:

  • COVID-19 patients during the seventh wave (Omicron BA.5) exhibited a lower risk of pneumonia compared to the sixth wave (Omicron BA.1/BA.2).
  • Despite reduced pneumonia risk, patients with comorbidities remain vulnerable to COVID-19-triggered exacerbations and mortality.

Keywords:
coronavirus disease 2019nosocomial infectionomicron variantpneumonia

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