![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
Which of the following can be inferred from the passage?
A.
there is already a case in which the virus is transmitted from person to person.
B.
american scientists take the pandemic more seriously than European ones.
C.
the effect of candidate vaccines can last more than one year.
D.
the manufacture of the vaccine must be authorized by safety authorities.