National Board of Health and Welfare, Sweden.
Swedish Intensive Care Registry, Värmland County Council, Karlstad, Sweden; Department of Cardiothoracic and Vascular Surgery, Heart Centre, Linköping University Hospital, Linköping, Sweden; Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden.
J Infect Public Health. 2024 Sep;17(9):102502. doi: 10.1016/j.jiph.2024.102502. Epub 2024 Jul 23.
The COVID-19 pandemic has had several phases with varying characteristics. We aimed to compare severity outcomes in different phases in a population with limited bias from risk factors.
In a nationwide observational study of all unvaccinated first-time COVID-19 test positive individuals in Sweden aged 18-64 years without comorbidity, from week 45 of 2020 to week 5 of 2022, variant periods with certain variants constituting ≥ 92 % of all whole genome-sequenced cases nationwide, were compared regarding hospitalisation (with main discharge code of COVID-19), severe illness (use of high-flow nasal oxygen or admission to intensive care unit), and death due to COVID-19. Logistic regression was used to estimate odds ratios (ORs) for comparison of these outcomes between variant periods, using adjustments for variant period, age, sex, country of birth, place of residence, income, and education.
The study included 789,133 individuals, including 15,145 hospitalised individuals. Among all individuals, the adjusted ORs for hospitalisation were 1.7 for the Alpha period vs the Pre-variant period (week 45-52 2020), 1.8 for the Delta period vs the Alpha period, and 0.1 for the Omicron period vs the Delta period (all comparisons significant). Among hospitalised individuals, the adjusted ORs for severe illness were 1.4 for the Alpha period vs the Pre-variant period, 1.7 for the Delta period vs the Alpha period, and 0.5 for the Omicron period vs the Delta period (all comparisons significant), and the adjusted ORs for death were 1.1 for the Alpha period vs the Pre-variant period (non-significant), 1.8 for the Delta period vs the Alpha period (significant), and 0.1 for the Omicron period vs the Delta period (non-significant).
In this population with limited bias from risk factors, vaccination, and previous infection, disease severity increased from the pre-variant to the Delta period and then decreased with the Omicron period, among all individuals and among hospitalised individuals. These severity outcome differences should be considered when the pandemic is evaluated.
COVID-19 大流行经历了几个阶段，每个阶段都有不同的特征。我们旨在比较不同阶段的严重结局，同时最大限度地减少来自风险因素的偏倚。
在一项针对瑞典所有未接种疫苗的首次 COVID-19 检测呈阳性的 18-64 岁无合并症的个体的全国性观察性研究中，从 2020 年第 45 周至 2022 年第 5 周，我们比较了具有特定变体的变体期，该变体在全国范围内占所有全基因组测序病例的≥92%，比较了住院治疗（主要出院代码为 COVID-19）、重症（使用高流量鼻氧或入住重症监护病房）和 COVID-19 死亡的情况。使用逻辑回归来估计变体期之间比较这些结果的优势比（OR），使用变体期、年龄、性别、出生地、居住地、收入和教育进行调整。
该研究纳入了 789133 名个体，包括 15145 名住院患者。在所有个体中，与前变体期（2020 年第 45-52 周）相比，Alpha 期住院的调整后 OR 为 1.7，Delta 期为 1.8，Omicron 期为 0.1（所有比较均有统计学意义）。在住院患者中，与 Alpha 期相比，Delta 期严重疾病的调整后 OR 为 1.4，Omicron 期为 0.5（所有比较均有统计学意义），Delta 期死亡的调整后 OR 为 1.8（有统计学意义），Omicron 期为 0.1（无统计学意义）。
在这个受风险因素、疫苗接种和既往感染影响较小的人群中，疾病严重程度从变体前时期到 Delta 时期增加，然后随着 Omicron 时期下降，所有个体和住院个体中均如此。在评估大流行时，应考虑这些严重结局差异。
