The are several posts already in the forums about vampires which may answer any questions you might have about them including https://chroniclesofelyria.com/forum/topic/12838/vampires.
Most questions about the game have either been covered by Dev Journals or by QnAs. You can find transcipts for the QnAs in the [Sticky] Q&A Compilation in GENERAL DISCUSSION .
The searchable website mentioned in https://chroniclesofelyria.com/forum/topic/9186/unofficial-compilation-of-coe-qa-website has easy to use reference links for use in the forums.
The searchable google docs compilation transcript at https://docs.google.com/document/d/1zeVus-edgr9Cnm4rTCDY_ShsDHzJXOdcUqmZ-PFPAso/edit?pref=2&pli=1 is quickest for highlighting and locating certain words.