卡介苗(Bacillus Calmette-Guérin，BCG)是目前唯一获准使用的预防结核病的疫苗。除结核分枝杆菌外，BCG对其他细菌、病毒和寄生虫等非同源病原体感染也具有非特异性的保护作用，还可用于一些肿瘤和自身免疫性疾病的免疫治疗，其机制研究表明与训练免疫有关。BCG诱导的训练免疫机制包括引起宿主天然免疫细胞代谢改变、表观遗传重编程及其对再刺激增强的免疫应答。BCG诱导的训练免疫具有抗多种病毒感染的保护作用，且与2019冠状病毒病的死亡率呈负相关，可能会削弱新发病原体在未来大流行中的影响。

Bacillus Calmette-Guérin (BCG) is the only licensed vaccine for the prevention of tuberculosis. In addition to tuberculosis, BCG has a non-specific protective effect on the prevention of non-homologous pathogens such as bacteria, viruses, parasites and so on. It is also used for immunotherapy of some tumors and autoimmune diseases. The non-specific protective mechanism of BCG is identified to be related to the induction of trained immunity. The mechanisms of BCG-induced trained immunity involve cell metabolism changes in host innate immune, epigenetic reprogramming, and enhanced immune responses to restimulation. BCG-induced trained immunity provides protective effects against multiple viral infections and is negatively associated with the mortality of coronavirus disease 2019 (COVID-19), which may have the impact on emerging pathogen pandemic in the future.