1. It belongs to a group of viruses that includes the smallpox virus (variola), the virus used in the smallpox vaccine (vaccinia), and the cowpox virus.
它属于一个包括天花病毒、在天花疫苗中采用的病毒和牛痘病毒的病毒组。
2. 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。