SARS-CoV-2 spike mRNA vaccines^1,2,3 mediate protection from severe disease as early as ten days after prime vaccination³, when neutralizing antibodies are hardly detectable^4,5,6. Vaccine-induced CD8⁺ T cells may therefore be the main mediators of protection at this early stage^7,8. The details of their induction, comparison to natural infection, and association with other arms of vaccine-induced immunity remain, however, incompletely understood. Here we show on a single-epitope level that a stable and fully functional CD8⁺ T cell response is vigorously mobilized one week after prime vaccination with bnt162b2, when circulating CD4⁺ T cells and neutralizing antibodies are still weakly detectable. Boost vaccination induced a robust expansion that generated highly differentiated effector CD8⁺ T cells; however, neither the functional capacity nor the memory precursor T cell pool was affected. Compared with natural infection, vaccine-induced early memory T cells exhibited similar functional capacities but a different subset distribution. Our results indicate that CD8⁺ T cells are important effector cells, are expanded in the early protection window after prime vaccination, precede maturation of other effector arms of vaccine-induced immunity and are stably maintained after boost vaccination.

SARS-CoV-2 刺突 mRNA 疫苗^1,2,3早在初次疫苗接种³后 10 天就可以介导对严重疾病的保护，当时几乎检测不到中和抗体^4,5,6。因此，疫苗诱导的 CD8 ⁺ T 细胞可能是早期保护的主要介质^7,8。然而，它们的诱导细节、与自然感染的比较以及与疫苗诱导免疫的其他武器的关联仍然不完全清楚。在这里，我们在单表位水平上显示，在用 bnt162b2 初次接种疫苗一周后，当循环^{CD4 +}T 细胞和中和抗体仍然微弱可检测。加强疫苗接种诱导了产生高度分化的效应 CD8 ⁺ T 细胞的强大扩增；然而，功能容量和记忆前体 T 细胞池都没有受到影响。与自然感染相比，疫苗诱导的早期记忆 T 细胞表现出相似的功能能力，但亚群分布不同。我们的结果表明，CD8 ⁺ T 细胞是重要的效应细胞，在初次接种后的早期保护窗口中扩增，在疫苗诱导免疫的其他效应臂成熟之前，并在加强接种后稳定维持。