a.

1. 牛痘的；疫苗的

n.

1. 牛痘苗；疫苗
   Up to this point in time, mankind has not been able to develop a vaccine for EBOLA.

   到目前为止，人类还没有发明遏制埃博拉的疫苗。

n.

1. an antigenic preparation used to stimulate the production of antibodies and provide immunity against a disease.
2. a program that detects computer viruses and prevents them from operating.