Let me explain.
So im sure your all aware that with dawnguard, vampires have a chance of attacking you if you enter or come close to the enterence of a town/city. I believe they are supposed/designed to stop (though this doesn't happen for everyone i think) with the completion of the MQ of dawnguard.
So if you have a character who still hasn't completed the DG MQ, and you also have dragonborn and therefore travel to this new island. Is there a chance vampires can attack your character on this new land? Or are vampire attacks only restriced to mainland skyrim?