这个致命的传染病，曾夺走了数百万人的生命，并带来许多苦难。 但是WHO展开根除天花的计划，服务范围无远弗届；只要有人居住的地方，都有专人将牛痘疫苗送达该处。

Smallpox had caused millions of deaths and much suffering for centuries, but once the agency set out to eradicate it, WHO personnel traveled the world to conduct a massive vaccination program.

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将近一个世纪，疫苗病毒(称牛痘)从手臂到手臂、从一个人身上转移到另一个人身上，问题是如何找到提供大量疫苗的方法，这个问题最终通过在牛胁腹部种植疫苗病毒的办法解决了。

The problem was to discover how to provide large amounts of vaccine. This was eventually solved by growing the vaccine virus on the flank of cows.

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But unlike the Cowpox virus, vaccinea, that we talked about before, this is the real disease causing agent.

但是同我们之前曾讨论过的,牛痘病毒疫苗的不同之处在于,这是可以直接致病的病毒

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Vaccination from cows, and that's where the first vaccine came from.

从牛身上获取牛痘疫苗,这是疫苗首次亮相

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