Idk about vampire lore but if they are invisible in mirror it means light passes through them undisturbed and therefore they shouldn't cast a shadow. But with the same logic they would be invisible altogether so it being exclusive to mirrors is a wild thing...
Regarding your previous commentary, I would like to remark that you neglected to properly adress the gentleman whom you were replying to.
I sure hope your father shows far better attitude when writing to the world wide web. I highly recommend to ask them for advice on how to improve your formal language.
or was the fish discovered by a convict surgeon?