I think Elan might actually stay himself.
Either because he already did take his „worst day”- which could easily be related to meeting his dad -to heart, so that the vampire wouldn't be much different (basically Elan acting like a vampire), or- more likely -he and his memories are so annoying that the vampire spirit (almost*) immediately leaves the building, resulting in pretty much the same.

*Well, considering the interaction with the host happens at the speed of thought it could appear like a long time for the spirit.