换而言之，我们曾经打败了天花。如果需要，我们必须准备和预防好再次打败它。

In other words, we've beaten smallpox once, but we must be ready and prepared to beat it again, if necessary.

youdao

换而言之，我们曾经打败了天花。如果需要，我们必须准备和预防好再次打败它。

In other words, we've beaten smallpox once, but we must be ready and prepared to beat it again, if necessary.

youdao