The Francis Crick Institute, London, United Kingdom.
National Institute for Health Research (NIHR) University College London Hospitals (UCLH) Biomedical Research Centre and NIHR UCLH Clinical Research Facility, London, United Kingdom.
PLoS One. 2024 Mar 21;19(3):e0294897. doi: 10.1371/journal.pone.0294897. eCollection 2024.
SARS-CoV-2 variant Omicron rapidly evolved over 2022, causing three waves of infection due to sub-variants BA.1, BA.2 and BA.4/5. We sought to characterise symptoms and viral loads over the course of COVID-19 infection with these sub-variants in otherwise-healthy, vaccinated, non-hospitalised adults, and compared data to infections with the preceding Delta variant of concern (VOC).
In a prospective, observational cohort study, healthy vaccinated UK adults who reported a positive polymerase chain reaction (PCR) or lateral flow test, self-swabbed on alternate weekdays until day 10. We compared participant-reported symptoms and viral load trajectories between infections caused by VOCs Delta and Omicron (sub-variants BA.1, BA.2 or BA.4/5), and tested for relationships between vaccine dose, symptoms and PCR cycle threshold (Ct) as a proxy for viral load using Chi-squared (χ2) and Wilcoxon tests.
563 infection episodes were reported among 491 participants. Across infection episodes, there was little variation in symptom burden (4 [IQR 3-5] symptoms) and duration (8 [IQR 6-11] days). Whilst symptom profiles differed among infections caused by Delta compared to Omicron sub-variants, symptom profiles were similar between Omicron sub-variants. Anosmia was reported more frequently in Delta infections after 2 doses compared with Omicron sub-variant infections after 3 doses, for example: 42% (25/60) of participants with Delta infection compared to 9% (6/67) with Omicron BA.4/5 (χ2 P < 0.001; OR 7.3 [95% CI 2.7-19.4]). Fever was less common with Delta (20/60 participants; 33%) than Omicron BA.4/5 (39/67; 58%; χ2 P = 0.008; OR 0.4 [CI 0.2-0.7]). Amongst infections with an Omicron sub-variants, symptoms of coryza, fatigue, cough and myalgia predominated. Viral load trajectories and peaks did not differ between Delta, and Omicron, irrespective of symptom severity (including asymptomatic participants), VOC or vaccination status. PCR Ct values were negatively associated with time since vaccination in participants infected with BA.1 (β = -0.05 (CI -0.10-0.01); P = 0.031); however, this trend was not observed in BA.2 or BA.4/5 infections.
Our study emphasises both the changing symptom profile of COVID-19 infections in the Omicron era, and ongoing transmission risk of Omicron sub-variants in vaccinated adults.
NCT04750356.
SARS-CoV-2 变体奥密克戎在 2022 年迅速进化，由于亚变体 BA.1、BA.2 和 BA.4/5，导致了三波感染。我们旨在描述这些亚变体引起的 COVID-19 感染过程中的症状和病毒载量，并将数据与之前的 Delta 变体（关注变体）进行比较。
在一项前瞻性、观察性队列研究中，报告 PCR 或侧向流动检测呈阳性的健康接种 UK 成年人，每隔一天自我采样，直到第 10 天。我们比较了由 VOC 引起的感染 Delta 和奥密克戎（亚变体 BA.1、BA.2 或 BA.4/5）的参与者报告的症状和病毒载量轨迹，并使用卡方（χ2）和 Wilcoxon 检验测试疫苗剂量、症状和 PCR 循环阈值（Ct）之间的关系，Ct 用作病毒载量的替代指标。
在 491 名参与者中报告了 563 次感染发作。在所有感染发作中，症状负担（4 [IQR 3-5] 症状）和持续时间（8 [IQR 6-11] 天）变化不大。虽然 Delta 引起的感染与奥密克戎亚变体引起的感染之间的症状谱有所不同，但奥密克戎亚变体之间的症状谱相似。与奥密克戎亚变体感染相比，接种 2 剂后 Delta 感染报告的嗅觉丧失更频繁，例如：与奥密克戎 BA.4/5 感染的 9%（6/67）相比，Delta 感染的 42%（25/60）参与者（χ2 P < 0.001；OR 7.3 [95% CI 2.7-19.4]）。Delta（20/60 名参与者；33%）感染的发热频率低于奥密克戎 BA.4/5（39/67；58%；χ2 P = 0.008；OR 0.4 [0.2-0.7]）。在奥密克戎亚变体感染中，鼻漏、疲劳、咳嗽和肌痛是主要症状。无论症状严重程度（包括无症状参与者）、VOC 或疫苗接种状态如何，Delta 和奥密克戎之间的病毒载量轨迹和峰值均无差异。PCR Ct 值与 BA.1 感染参与者的接种时间呈负相关（β = -0.05（CI -0.10-0.01）；P = 0.031）；然而，这种趋势在 BA.2 或 BA.4/5 感染中并未观察到。
我们的研究强调了奥密克戎时代 COVID-19 感染症状谱的变化，以及接种疫苗的成年人中奥密克戎亚变体持续传播的风险。
NCT04750356。
