Usually it's done by taking all or part of the infectious agent, and showing them to your immune system in some way.

通常它会带着全部或部分抗原介质,并以某种方式呈递给你的免疫系统

耶鲁公开课 - 生物医学工程探索课程节选

So, it first infects you because you breathe in some of the infectious agent.

所以,只要吸入病原体,你就会被感染

耶鲁公开课 - 生物医学工程探索课程节选

Usually it involves pieces of the infectious agent itself, to cause that engagement.

通常疫苗自身也包含部分传染性介质,以便达成匹配

耶鲁公开课 - 生物医学工程探索课程节选