Department of Health Data Science, Institute of Population Health, University of Liverpool, Liverpool, United Kingdom.
Department of Public Health, Liverpool City Council, Liverpool, United Kingdom.
Euro Surveill. 2023 Jan;28(4). doi: 10.2807/1560-7917.ES.2023.28.4.2200129.
BackgroundThe PCR quantification cycle (C) is a proxy measure of the viral load of a SARS-CoV-2-infected individual.AimTo investigate if C values vary according to different population characteristics, in particular demographic ones, and within the COVID-19 pandemic context, notably the SARS-CoV-2 type/variant individuals get infected with.MethodsWe considered all positive PCR results from Cheshire and Merseyside, England, between 6 November 2020 and 8 September 2021. C distributions were inspected with Kernel density estimates. Multivariable quantile regression models assessed associations between people's features and C.ResultsWe report C values for 188,821 SARS-CoV-2 positive individuals. Median Cs increased with decreasing age for suspected wild-type virus and Alpha variant infections, but less so, if not, for Delta. For example, compared to 30-39-year-olds (median age group), 5-11-year-olds exhibited 1.8 (95% CI: 1.5 to 2.1), 2.2 (95% CI: 1.8 to 2.6) and 0.8 (95% CI: 0.6 to 0.9) higher median Cs for suspected wild-type, Alpha and Delta positives, respectively, in multivariable analysis. 12-18-year-olds also had higher Cs for wild-type and Alpha positives, however, not for Delta. Overall, in univariable analysis, suspected Delta positives reported 2.8 lower median Cs than wild-type positives (95% CI: 2.7 to 2.8; p < 0.001). Suspected Alpha positives had 1.5 (95% CI: 1.4 to 1.5; p < 0.001) lower median Cs than wild type.ConclusionsWild-type- or Alpha-infected school-aged children (5-11-year-olds) might transmit less than adults (> 18 years old), but have greater mixing exposures. Smaller differences in viral loads with age occurred in suspected Delta infections. Suspected-Alpha- or Delta-infections involved higher viral loads than wild type, suggesting increased transmission risk. COVID-19 control strategies should consider age and dominant variant.
背景
聚合酶链式反应（PCR）定量循环（C）是 SARS-CoV-2 感染个体病毒载量的替代测量指标。
目的
在 COVID-19 大流行背景下，特别是在 SARS-CoV-2 个体感染的类型/变体方面，调查 C 值是否因不同的人口特征，尤其是人口统计学特征而有所不同。
方法
我们考虑了 2020 年 11 月 6 日至 2021 年 9 月 8 日期间英格兰柴郡和默西塞德郡的所有阳性 PCR 结果。使用核密度估计值检查 C 的分布。多变量分位数回归模型评估了人群特征与 C 之间的关联。
结果
我们报告了 188,821 例 SARS-CoV-2 阳性个体的 C 值。疑似野生型病毒和 Alpha 变异感染的 C 值随年龄的降低而增加，但 Delta 感染的 C 值则不然。例如，与 30-39 岁（中位数年龄组）相比，5-11 岁儿童的疑似野生型、Alpha 和 Delta 阳性的中位数 C 值分别高出 1.8（95%置信区间：1.5-2.1）、2.2（95%置信区间：1.8-2.6）和 0.8（95%置信区间：0.6-0.9）。12-18 岁的儿童在野生型和 Alpha 阳性时也有更高的 C 值，但在 Delta 阳性时则没有。总体而言，在单变量分析中，疑似 Delta 阳性的人比疑似野生型阳性的人报告的中位数 C 值低 2.8（95%置信区间：2.7-2.8；p<0.001）。疑似 Alpha 阳性的人的中位数 C 值比野生型低 1.5（95%置信区间：1.4-1.5；p<0.001）。
结论
感染野生型或 Alpha 的学龄儿童（5-11 岁）的传播可能比成年人（>18 岁）少，但混合暴露更多。在疑似 Delta 感染中，年龄与病毒载量之间的差异较小。疑似 Alpha 或 Delta 感染的病毒载量高于野生型，表明传播风险增加。COVID-19 控制策略应考虑年龄和主要变异。
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