即使在感染你的时候，感冒病毒也会发生变异，而且新的病毒毒株经常出现，以至于当制药商研制出针对其中一种变异的疫苗时，血清已经过时了。

Colds mutate even while they're infecting you, and new strains pop up so often that by the time drug-makers create a vaccine against one variation, the serum is already out of date.

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这种疫苗是根据最常见的轮状病毒毒株制成的，而且在两年的时间里也能很好地保护人体不受其它一些毒株的感染。

The vaccine is derived from the most commonly circulating strain of rotavirus, and also offered good protection against some other strains across the two-year period.

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流感病毒不断发生基因变化并需要符合正在传播的流感毒株的疫苗以便产生作用，所以每年必须调整季节性流感疫苗。

Influenza viruses constantly undergo genetic changes and require vaccines that match the circulating influenza strains to be effective, so seasonal influenza vaccines have to be modified annually.

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We talked about attenuating in the laboratory, using cell culture techniques and what we know about mutating viruses.

我们讲过实验室中,利用细胞培养技术培养减毒疫苗,以及我们所了解的减毒病毒

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He produced an oral polio vaccine from an attenuated virus.

他利用减毒病毒制得口服小儿麻痹症疫苗

耶鲁公开课 - 生物医学工程探索课程节选

This was not a naturally occurring attenuated virus as used in smallpox, but a virus that was attenuated in the laboratory, basically by propagating it in culture and looking for mutants that were formed as you propagated this virus under different experimental conditions.

这不是在制造天花疫苗时,使用的那种天然减毒病毒,而是一种在实验室中被人工弱化的病毒,基本上是通过在细胞中培养繁殖后,从这些培养出来的病毒中挑选出,不同实验环境下的变异体

耶鲁公开课 - 生物医学工程探索课程节选