T cell reactivity against SARS-CoV-2 was observed in unexposed people; however, the source and clinical relevance of the reactivity remains unknown. It is speculated that this reflects T cell memory to circulating ‘common cold’ coronaviruses. It will be important to define specificities of these T cells and assess their association with COVID-19 disease severity and vaccine responses. Recent studies have shown T cell reactivity to SARS-CoV-2 in 20–50% of unexposed individuals; it is speculated that this is due to T cell memory to common cold coronaviruses. Here, Crotty and Sette discuss the potential implications of these findings for disease severity, herd immunity and vaccine development.

中文翻译：

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对 SARS-CoV-2 的预先存在的免疫力：已知和未知。

在未接触过 SARS-CoV-2 的人群中观察到 T 细胞的反应性；然而，该反应的来源和临床相关性仍然未知。据推测，这反映了 T 细胞对循环的“普通感冒”冠状病毒的记忆。定义这些 T 细胞的特异性并评估它们与 COVID-19 疾病严重程度和疫苗反应的关联非常重要。最近的研究表明，20-50% 的未暴露个体中 T 细胞对 SARS-CoV-2 具有反应性；据推测，这是由于T细胞对普通感冒冠状病毒的记忆所致。在这里，克罗蒂和塞特讨论了这些发现对疾病严重程度、群体免疫和疫苗开发的潜在影响。