Effect of Covid-19 Vaccination on Transmission of Alpha and Delta Variants.
Effect of Covid-19 Vaccination on Transmission of Alpha and Delta Variants.
复制标题
DOI：
10.1056/nejmoa2116597
复制
发表时间：
2022-02-24
期刊：
影响因子：
--
通讯作者：
Peto TEA
中科院分区：
文献类型：
--
作者：
Eyre DW;Taylor D;Purver M;Chapman D;Fowler T;Pouwels KB;Walker AS;Peto TEA
在严重急性呼吸综合征冠状病毒2型（SARS-CoV-2）的B.1.617.2（delta）变异体出现之前，接种疫苗可能通过降低病毒载量来减少SARS-CoV-2从接种疫苗的感染者中的传播。尽管接种疫苗仍然降低了感染风险，但感染德尔塔变异体的接种疫苗和未接种疫苗者的病毒载量相似，这使人对接种疫苗预防传播的程度产生了疑问。我们使用来自英国的接触测试数据进行了一项回顾性观察性队列研究，该研究涉及SARS-CoV-2感染成人索引患者的成人接触者。我们使用多变量Poisson回归来研究传播与索引患者和接触者的疫苗接种状态之间的关联，并确定这些关联如何随B.1.1.7（α）和δ变体以及自第二次疫苗接种以来的时间而变化。在108，498名指数患者的146，243名受检接触者中，54，667名（37%）SARS-CoV-2聚合酶链反应（PCR）检测呈阳性。在感染α变异体的索引患者中，两次接种BNT 162 b2或ChAdOx 1 nCoV-19（也称为AZD 1222）与未接种疫苗相比，与接触者中PCR阳性率降低独立相关。（BNT 162 b2的校正率比为0.32; 95%置信区间[CI]为0.21 - 0.48; ChAdOx 1 nCoV-19为0.48; 95% CI为0.30 - 0.78）。与疫苗相关的δ变异体传播减少小于α变异体，两次BNT 162 b2疫苗接种后δ变异体传播减少更大。（与未接种疫苗比较的校正率比，0.50; 95% CI，0.39 - 0.65）（校正率比，0.76; 95% CI，0.70 - 0.82）。索引患者中的循环阈值（Ct）值（指示病毒载量）的变化解释了两种变体传播中疫苗相关减少的7%至23%。在第二次疫苗接种后，δ变体传播的减少随着时间的推移而下降，在接受ChAdOx 1 nCoV-19的索引患者中，到12周时达到与未接种疫苗的人相似的水平，并且在接受BNT 162 b2的患者中大幅减弱。在第二次接种疫苗后的3个月内，接触者的保护作用也有所下降。与α变体相比，疫苗接种与δ变体传播的较小减少相关，并且疫苗接种的效果随着时间的推移而降低。PCR Ct值在诊断的索引患者只有部分解释减少传输。（由英国资助。政府卫生和社会保健部及其他部门。
Before the emergence of the B.1.617.2 (delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), vaccination reduced transmission of SARS-CoV-2 from vaccinated persons who became infected, potentially by reducing viral loads. Although vaccination still lowers the risk of infection, similar viral loads in vaccinated and unvaccinated persons who are infected with the delta variant call into question the degree to which vaccination prevents transmission. We used contact-testing data from England to perform a retrospective observational cohort study involving adult contacts of SARS-CoV-2–infected adult index patients. We used multivariable Poisson regression to investigate associations between transmission and the vaccination status of index patients and contacts and to determine how these associations varied with the B.1.1.7 (alpha) and delta variants and time since the second vaccination. Among 146,243 tested contacts of 108,498 index patients, 54,667 (37%) had positive SARS-CoV-2 polymerase-chain-reaction (PCR) tests. In index patients who became infected with the alpha variant, two vaccinations with either BNT162b2 or ChAdOx1 nCoV-19 (also known as AZD1222), as compared with no vaccination, were independently associated with reduced PCR positivity in contacts (adjusted rate ratio with BNT162b2, 0.32; 95% confidence interval [CI], 0.21 to 0.48; and with ChAdOx1 nCoV-19, 0.48; 95% CI, 0.30 to 0.78). Vaccine-associated reductions in transmission of the delta variant were smaller than those with the alpha variant, and reductions in transmission of the delta variant after two BNT162b2 vaccinations were greater (adjusted rate ratio for the comparison with no vaccination, 0.50; 95% CI, 0.39 to 0.65) than after two ChAdOx1 nCoV-19 vaccinations (adjusted rate ratio, 0.76; 95% CI, 0.70 to 0.82). Variation in cycle-threshold (Ct) values (indicative of viral load) in index patients explained 7 to 23% of vaccine-associated reductions in transmission of the two variants. The reductions in transmission of the delta variant declined over time after the second vaccination, reaching levels that were similar to those in unvaccinated persons by 12 weeks in index patients who had received ChAdOx1 nCoV-19 and attenuating substantially in those who had received BNT162b2. Protection in contacts also declined in the 3-month period after the second vaccination. Vaccination was associated with a smaller reduction in transmission of the delta variant than of the alpha variant, and the effects of vaccination decreased over time. PCR Ct values at diagnosis of the index patient only partially explained decreased transmission. (Funded by the U.K. Government Department of Health and Social Care and others.)