I really don't know, although I reckon they probably wouldn't mind as long as it wouldn't affect your working ability. Although you may be better off transitioning afterwards, or beforehand.
I'd say get in touch with somebody who actually knows, they can tell you for sure.
Check out Anne Rice. She has written many novels based around Vampires. As far as I know, her novels were written quite a while ago and some may be slightly difficult to find but my dad (loves vampire novels) And highly recommends her writing.