Allen Hester, Vusirikala Amoolya, Flannagan Joe, Twohig Katherine A, Zaidi Asad, Chudasama Dimple, Lamagni Theresa, Groves Natalie, Turner Charlie, Rawlinson Christopher, Lopez-Bernal Jamie, Harris Ross, Charlett Andre, Dabrera Gavin, Kall Meaghan
National Infection Service, Public Health England, Colindale, London, NW9 5EQ, UK.
Lancet Reg Health Eur. 2022 Jan;12:100252. doi: 10.1016/j.lanepe.2021.100252. Epub 2021 Oct 28.
The SARS-CoV-2 Delta variant (B.1.617.2), first detected in India, has rapidly become the dominant variant in England. Early reports suggest this variant has an increased growth rate suggesting increased transmissibility. This study indirectly assessed differences in transmissibility between the emergent Delta variant compared to the previously dominant Alpha variant (B.1.1.7).
A matched case-control study was conducted to estimate the odds of household transmission (≥ 2 cases within 14 days) for Delta variant index cases compared with Alpha cases. Cases were derived from national surveillance data (March to June 2021). One-to-two matching was undertaken on geographical location of residence, time period of testing and property type, and a multivariable conditional logistic regression model was used for analysis.
In total 5,976 genomically sequenced index cases in household clusters were matched to 11,952 sporadic index cases (single case within a household). 43.3% (n=2,586) of cases in household clusters were confirmed Delta variant compared to 40.4% (n= 4,824) of sporadic cases. The odds ratio of household transmission was 1.70 among Delta variant cases (95% CI 1.48-1.95, p <0.001) compared to Alpha cases after adjusting for age, sex, ethnicity, index of multiple deprivation (IMD), number of household contacts and vaccination status of index case.
We found evidence of increased household transmission of SARS-CoV-2 Delta variant, potentially explaining its success at displacing Alpha variant as the dominant strain in England. With the Delta variant now having been detected in many countries worldwide, the understanding of the transmissibility of this variant is important for informing infection prevention and control policies internationally.
严重急性呼吸综合征冠状病毒2（SARS-CoV-2）的德尔塔变种（B.1.617.2）最早在印度被发现，迅速成为英国的主要变种。早期报告表明，该变种生长速度加快，意味着传播性增强。本研究间接评估了新出现的德尔塔变种与先前占主导地位的阿尔法变种（B.1.1.7）之间传播性的差异。
开展一项配对病例对照研究，以估计德尔塔变种索引病例与阿尔法病例相比发生家庭传播（14天内≥2例）的几率。病例来自国家监测数据（2021年3月至6月）。根据居住地理位置、检测时间段和房产类型进行1:2配对，并使用多变量条件逻辑回归模型进行分析。
家庭聚集性病例中共有5976例经基因组测序的索引病例与11952例散发索引病例（家庭内单例）配对。家庭聚集性病例中43.3%（n = 2586）被确认为德尔塔变种，而散发病例中这一比例为40.4%（n = 4824）。在对年龄、性别、种族、多重贫困指数（IMD）、家庭接触者数量和索引病例的疫苗接种状况进行调整后，德尔塔变种病例的家庭传播优势比为1.70（95%置信区间1.48 - 1.95，p<0.001），高于阿尔法病例。
我们发现有证据表明SARS-CoV-2德尔塔变种的家庭传播有所增加，这可能解释了它在英国取代阿尔法变种成为主要毒株的原因。鉴于目前全球许多国家都已检测到德尔塔变种，了解该变种的传播性对于制定国际感染预防和控制政策至关重要。
