Well, this shows what happened in the period after this vaccine was introduced into the general population so that would have been in 1954.

这表明了,疫苗在一九五四年,引入大众后的一段时间内,发生了什么样的情况

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and that can be something that you pay off for a long time.

可能毕业后的很长一段时间内都在偿还欠下的贷款。

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