None of these do we have vaccines for, and it's turned out that sexually transmitted diseases for a variety of reasons, we'll come back to later, are particularly difficult to develop vaccines for.

这些病我们都没有疫苗,已经证明,对于性传播疾病,有很多原因使得,我们稍后回来再讲,针对这类疾病的疫苗特别难做出来

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