要旨
...【背景】COVID–19は変異株ごとに感染性や毒性が異なる。デルタ株による第5波では重症者，死者数が増加した。第5波における重症患者の臨床的特徴と治療成績を明らかにすることを目的とした。【方法】2020年2月から2021年9月までに当院でCOVID–19による呼吸不全で人工呼吸器を使用した53例を対象とした。2020年2月から2021年6月までの第1～4波と2021年7月から10月までの第5波の2群に分け，後方視的に全生存期間を比較した。観察期間中央値は90日。【結果】第1～4波は40例，第5波は13例，全例ワクチン未接種であった。第1～4波ではL452R変異は検出されず，第5波では10例（77%）だった。年齢中央値は68歳vs. 56歳（第1～4波vs. 第5波，P<0.01），BMIは27 vs. 30（P=0.02），P/F比は136 vs. 80（P<0.01），入院までの日数は6日vs. 8日（P=0.03）と有意差を認めた。全生存期間では90日生存率が71% vs. 37%（P<0.01）と第5波が予後不良であった。多変量解析では第1～4波に対して第5波は生存率悪化に影響を及ぼしていた（HR 6.35，95%CI 1.96–20.6）。【結語】第1～4波に比べ第5波の重症COVID–19患者は若年にも関わらず，救命率が低かった。デルタ株の影響，搬送困難による治療の遅れが示唆された。
ABSTRACT
Background: Spike protein mutations are known to affect the infectivity and virulence of coronavirus disease 2019 (COVID–19). The number of severe COVID–19 cases and deaths has increased due to the Delta variant. We aimed to evaluate the clinical characteristics and treatment outcomes of severe COVID–19 patients.
Methods: Fifty–three consecutively presenting patients requiring mechanical ventilation for respiratory failure due to COVID–19 were seen at our institution between February 2020 and October 2021. We divided these patients into two groups: 13 patients admitted from July to October 2021 (the Delta period) and 40 patients admitted from February 2020 to June 2021 (the non–Delta period). We retrospectively compared overall survival between these groups (median observation period, 90 days).
Results: All patients were unvaccinated. No L452R mutations were detected during the non–Delta period, whereas 10 (77%) such mutations were detected during the Delta period. Patient characteristics (non–Delta vs. Delta) were as follows: age, 68 vs. 56 years (P<0.01); body mass index, 27 vs. 30kg/m2 (P=0.02); P/F ratio (PaO2/FiO2), 136 vs. 80 (P<0.01); and days to hospitalization, 6 vs. 8 days (P=0.03). The 90–day survival rate was lower in the Delta group (71% vs. 37%, P<0.01). Multivariate analysis showed that the Delta variant was an independent unfavorable prognostic factor (hazard ratio 6.35, 95% confidence interval 1.96–20.6).
Conclusion: Despite a younger patient age, survival rate was significantly worse in the Delta period. This is probably due to the infectivity and virulence of the Delta variant and delays in treatment caused by difficulty in transportation.
