BioNTech, Mainz, Germany.
South African Medical Research Council Vaccines and Infectious Diseases Analytics Research Unit, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Front Immunol. 2023 May 23;14:1130539. doi: 10.3389/fimmu.2023.1130539. eCollection 2023.
The highly transmissible Omicron (B.1.1.529) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first detected in late 2021. Initial Omicron waves were primarily made up of sub-lineages BA.1 and/or BA.2, BA.4, and BA.5 subsequently became dominant in mid-2022, and several descendants of these sub-lineages have since emerged. Omicron infections have generally caused less severe disease on average than those caused by earlier variants of concern in healthy adult populations, at least, in part, due to increased population immunity. Nevertheless, healthcare systems in many countries, particularly those with low population immunity, have been overwhelmed by unprecedented surges in disease prevalence during Omicron waves. Pediatric admissions were also higher during Omicron waves compared with waves of previous variants of concern. All Omicron sub-lineages exhibit partial escape from wild-type (Wuhan-Hu 1) spike-based vaccine-elicited neutralizing antibodies, with sub-lineages with more enhanced immuno-evasive properties emerging over time. Evaluating vaccine effectiveness (VE) against Omicron sub-lineages has become challenging against a complex background of varying vaccine coverage, vaccine platforms, prior infection rates, and hybrid immunity. Original messenger RNA vaccine booster doses substantially improved VE against BA.1 or BA.2 symptomatic disease. However, protection against symptomatic disease waned, with reductions detected from 2 months after booster administration. While original vaccine-elicited CD8 and CD4 T-cell responses cross-recognize Omicron sub-lineages, thereby retaining protection against severe outcomes, variant-adapted vaccines are required to expand the breadth of B-cell responses and improve durability of protection. Variant-adapted vaccines were rolled out in late 2022 to increase overall protection against symptomatic and severe infections caused by Omicron sub-lineages and antigenically aligned variants with enhanced immune escape mechanisms.
高度传染性的严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 的奥密克戎 (B.1.1.529) 变体于 2021 年底首次被发现。最初的奥密克戎浪潮主要由亚系 BA.1 和/或 BA.2、BA.4 和 BA.5 组成，随后在 2022 年年中成为主导，此后这些亚系的几个后代已经出现。与之前令人关注的变异株相比，奥密克戎感染在健康成年人群中平均导致的疾病严重程度较低，至少部分原因是人群免疫力增强。然而，许多国家的医疗保健系统，特别是那些人群免疫力较低的国家，在奥密克戎浪潮期间，疾病流行率的空前飙升使医疗系统不堪重负。在奥密克戎浪潮期间，儿科住院人数也高于之前令人关注的变异株浪潮。所有奥密克戎亚系都表现出对野生型（武汉-Hu1）刺突蛋白为基础的疫苗诱导中和抗体的部分逃逸，随着时间的推移，免疫逃避特性增强的亚系不断出现。在不断变化的疫苗接种率、疫苗平台、既往感染率和混合免疫的复杂背景下，评估针对奥密克戎亚系的疫苗有效性 (VE) 变得具有挑战性。原始信使 RNA 疫苗加强剂量大大提高了针对 BA.1 或 BA.2 有症状疾病的 VE。然而，对有症状疾病的保护作用减弱，在加强接种后 2 个月检测到保护作用下降。虽然原始疫苗诱导的 CD8 和 CD4 T 细胞反应交叉识别奥密克戎亚系，从而保持对严重结果的保护作用，但需要变体适应性疫苗来扩大 B 细胞反应的广度并提高保护作用的持久性。变体适应性疫苗于 2022 年底推出，以提高针对奥密克戎亚系和具有增强免疫逃逸机制的抗原性对齐变体引起的有症状和严重感染的总体保护作用。
