From the National COVID-19 Epidemiology Cell, National Infection Service, Public Health England, Colindale, London, United Kingdom.
Epidemiology. 2022 Jul 1;33(4):465-469. doi: 10.1097/EDE.0000000000001497. Epub 2022 May 3.
The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.7 variant in England in 2020 and subsequent global spread emphasized the need to understand epidemiologic characteristics of SARS-CoV-2 variants. A diagnostic proxy for this variant, referred to as S-gene target failure, provided a rich dataset to assess transmissibility of the variant in an analysis of clustering in residential settings.
We used a pair-matched case-control study design to estimate odds of onward transmission within households with S-gene target failure index cases versus nontarget failure index cases. We defined cases as the index in a household cluster (clustered case) and controls as a case with no subsequent household cluster (sporadic). We matched clustered and sporadic cases one-to-one on specimen week, geography, and property type. We used conditional logistic regression, adjusting for age, sex, ethnicity, and symptom status, to assess odds of residential clustering.
Our study population comprised 57,244 individuals with specimen dates from 23 November 2020 to 4 January 2021. Crude analysis yielded 54% increased odds (odds ratio [OR] = 1.5; 95% confidence interval [CI] = 1.5, 1.6) of residential clustering associated with S-gene target failure; the association remained in the fully adjusted model (OR = 1.6, 95% CI = 1.5, 1.6). Stratified analyses by region showed increased odds of residential clustering associated with target failure in all regions apart from the Southwest, where we observed lower precision. Similar adjusted odds ratios with precise confidence intervals remained in stratified analyses by property category.
We observed increased odds in all property types, consistent with greater transmissibility of the B.1.1.7 variant in this high-risk setting.
2020 年，严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）B.1.1.7 变异株在英国出现，随后在全球传播，这凸显了了解 SARS-CoV-2 变异株的流行病学特征的必要性。该变异株的一个诊断替代指标，称为 S 基因靶标失败，为评估变异株在住宅环境中聚集的传染性提供了丰富的数据集。
我们使用配对病例对照研究设计来估计具有 S 基因靶标失败指数病例的家庭中与非靶标失败指数病例相比的传播几率。我们将病例定义为家庭群集中的索引（聚集病例），将对照定义为没有后续家庭群集的病例（散发性病例）。我们按标本周、地理位置和物业类型将聚集病例和散发性病例一对一匹配。我们使用条件逻辑回归，调整年龄、性别、种族和症状状态，以评估住宅聚集的几率。
我们的研究人群包括 57244 名在 2020 年 11 月 23 日至 2021 年 1 月 4 日期间有样本日期的个体。初步分析得出，S 基因靶标失败与住宅聚集的几率增加了 54%（比值比[OR] = 1.5；95%置信区间[CI] = 1.5, 1.6）；在完全调整的模型中，这种关联仍然存在（OR = 1.6，95%CI = 1.5，1.6）。按地区的分层分析显示，除西南部外，所有地区与目标失败相关的住宅聚集几率都有所增加，而在西南部地区，我们观察到的精度较低。在按物业类型进行的分层分析中，调整后的比值比和精确置信区间仍然相似。
我们观察到所有物业类型的几率都增加了，这与 B.1.1.7 变异株在这种高风险环境中的传染性增强一致。
