Memory cells are long lasting cells that remember this exposure and can respond very quickly on second exposure.

记忆细胞可以长时间记忆与抗原的接触,并在再次免疫中迅速做出应答

耶鲁公开课 - 生物医学工程探索课程节选

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