We did a test-negative, case-control study at two medical research centres in Faridabad, India. All individuals who had a positive RT-PCR test for SARS-CoV-2 infection between April 1, 2021, and May 31, 2021, were included as cases and individuals who had a negative RT-PCR test were included as controls after matching with cases on calendar week of RT-PCR test. The primary outcome was effectiveness of complete vaccination with the ChAdOx1 nCoV-19 vaccine against laboratory-confirmed SARS-CoV-2 infection. The secondary outcomes were effectiveness of a single dose against SARS-CoV-2 infection and effectiveness of a single dose and complete vaccination against moderate-to-severe disease among infected individuals. Additionally, we tested in-vitro live-virus neutralisation and T-cell immune responses to the spike protein of the wild-type SARS-CoV-2 and VOCs among healthy (anti-nucleocapsid antibody negative) recipients of the ChAdOx1 nCoV-19 vaccine.
Of 2379 cases of confirmed SARS-CoV-2 infection, 85 (3·6%) were fully vaccinated compared with 168 (8·5%) of 1981 controls (adjusted OR [aOR] 0·37 [95% CI 0·28-0·48]), giving a vaccine effectiveness against SARS-CoV-2 infection of 63·1% (95% CI 51·5-72·1). 157 (6·4%) of 2451 of cases and 181 (9·1%) of 1994) controls had received a single dose of the ChAdOx1 nCoV-19 vaccine (aOR 0·54 [95% CI 0·42-0·68]), thus vaccine effectiveness of a single dose against SARS-CoV-2 infection was 46·2% (95% CI 31·6-57·7). One of 84 cases with moderate-to-severe COVID-19 was fully vaccinated compared with 84 of 2295 cases with mild COVID-19 (aOR 0·19 [95% CI 0·01-0·90]), giving a vaccine effectiveness of complete vaccination against moderate-to-severe disease of 81·5% (95% CI 9·9-99·0). The effectiveness of a single dose against moderate-to-severe disease was 79·2% (95% CI 46·1-94·0); four of 87 individuals with moderate-to-severe COVID-19 had received a single dose compared with 153 of 2364 participants with mild disease (aOR 0·20 [95% CI 0·06-0·54]). Among 49 healthy, fully vaccinated individuals, neutralising antibody responses were lower against the alpha (B.1.1.7; geometric mean titre 244·7 [95% CI 151·8-394·4]), beta (B.1.351; 97·6 [61·2-155·8]), kappa (B.1.617.1; 112·8 [72·7-175·0]), and delta (88·4 [61·2-127·8]) variants than against wild-type SARS-CoV-2 (599·4 [376·9-953·2]). However, the antigen-specific CD4 and CD8 T-cell responses were conserved against both the delta variant and wild-type SARS-CoV-2.
The ChAdOx1 nCoV-19 vaccine remained effective against moderate-to-severe COVID-19, even during a surge that was dominated by the highly transmissible delta variant of SARS-CoV-2. Spike-specific T-cell responses were maintained against the delta variant. Such cellular immune protection might compensate for waning humoral immunity.
Department of Biotechnology India, Council of Scientific and Industrial Research India, and Fondation Botnar.
我们的检测结果呈阴性,在法里达巴德的两个医学研究中心进行的病例对照研究,印度。在2021年4月1日至2021年5月31日期间,所有SARS-CoV-2感染的RT-PCR检测阳性的个体都被纳入病例,RT-PCR检测阴性的个体在RT-PCR检测的日历周与病例匹配后被纳入对照。主要结果是用ChAdOx1nCoV-19疫苗完全接种对实验室确认的SARS-CoV-2感染的有效性。次要结果是单剂量对SARS-CoV-2感染的有效性以及单剂量和完全疫苗接种对感染个体中中度至重度疾病的有效性。此外,我们测试了ChAdOx1nCoV-19疫苗健康(抗核衣壳抗体阴性)受者对野生型SARS-CoV-2和VOCs刺突蛋白的体外活病毒中和和T细胞免疫应答.
在2379例确诊的SARS-CoV-2感染病例中,85(3·6%)完全接种疫苗,而1981年对照组为168(8·5%)(调整后的OR[aOR]0·37[95%CI0·28-0·48]),疫苗对SARS-CoV-2感染的有效性为63·1%(95%CI51·5-72·1)。2451例病例中的157例(6·4%)和1994年的181例(9·1%)对照接受了单剂量的ChAdOx1nCoV-19疫苗(aOR0·54[95%CI0·42-0·68]),因此,单剂量抗SARS-CoV-2感染的疫苗效力为46·2%(95%CI31·6-57·7).84例中重度COVID-19患者中有1例完全接种了疫苗,而2295例轻度COVID-19患者中有84例接种了疫苗(aOR0·19[95%CI0·01-0·90]),对中度至重度疾病完全接种疫苗的疫苗效力为81·5%(95%CI9·9-99·0)。单剂量对中度至重度疾病的有效性为79·2%(95%CI46·1-94·0);87名中度至重度COVID-19患者中有4人接受了单剂量治疗,而2364名轻度疾病患者中有153人接受了单剂量治疗(aOR0·20[95%CI0·06-0·54])。在健康的49人中,完全接种疫苗的人,中和抗体对α的反应较低(B.1.1.7;几何平均滴度244·7[95%CI151·8-394·4]),贝塔(B.1.351;97·6[61·2-155·8]),卡帕(B.1.617.1;112·8[72·7-175·0]),和δ(88·4[61·2-127·8])变体比野生型SARS-CoV-2(599·4[376·9-953·2])。然而,抗原特异性CD4和CD8T细胞应答对δ变体和野生型SARS-CoV-2均保守.
ChAdOx1nCoV-19疫苗对中度至重度COVID-19仍然有效,即使在由高度传染性的SARS-CoV-2δ变体主导的激增期间。针对δ变体维持刺突特异性T细胞应答。这种细胞免疫保护可能会弥补体液免疫的减弱。
印度生物技术部,印度科学与工业研究委员会,还有Botnar基金会.