If this was tetanus, you got this tetanus vaccine when you were young; you get a boost every five or ten years because your antibody levels are starting to fall.

以破伤风为例,小时候,你接种过破伤风的疫苗,每隔五年或十年要再接种一次,这是因为体内的抗体浓度会下降

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None of you got smallpox vaccinations, because once a country was certified to be smallpox free, there was no reason to-- there was no reason to vaccinate people any longer.

你们当中没人接种过天花疫苗,因为一旦一个国家确认不再有天花,就没有理由,就没有理由再给人们接种

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So, if you were someone that was getting it after it had been passed through many people, you wouldn't have as strong or as lengthy a protection as the first individual did.

如果一个疫苗经过很多人的传递,再接种到你身上,你不会获得像第一个接受疫苗的人,那样强效持久的免疫效果

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