Some, like the smallpox vaccine on one exposure generates a very high response that lasts for many years so you don't need a boost.

有一些疫苗,比如接触一次天花疫苗后,人体就能产生高水平的免疫应答,并持续很多年,所以无需再次接种

耶鲁公开课 - 生物医学工程探索课程节选

Others generate a weaker response that does require boosting.

还有一些疫苗产生的免疫应答较弱,这种疫苗就需要再次接种

耶鲁公开课 - 生物医学工程探索课程节选

Here, I've just picked a couple of the pictures that I showed you last time when we were talking about cell communication in the immune system, What happens after the vaccine is introduced into your body is that it initiates cellular events.

我挑选了,我上次给你们展示的几幅图片,当我们讨论到,免疫系统中的细胞沟通时,讲到过当人体接种疫苗之后,能够触发,细胞活动

耶鲁公开课 - 生物医学工程探索课程节选