The vaccinia virus is a non-dangerous virus used in the smallpox vaccine because it is related to the variola virus, which is the agent of smallpox.
痘苗病毒使用在牛痘苗时是无害的，因为它与作为传播天花媒介物的天花病毒相关。
The vaccinia virus is a non-dangerous virus used in the smallpox vaccine because it is related to the variola virus, which is the agent of smallpox.
痘苗病毒使用在牛痘苗时是无害的，因为它与作为传播天花媒介物的天花病毒相关。
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