I mean, if they are noob, sure, warn them.I'd say "That wish is going to screw your character over hard if you make it. There is no scenario where you just get vampire powers and carry on like normal. Do you want to proceed?"
But if it’s not their first rodeo, they should be aware of how wishes work not just in X version of D&D rules, but pretty much all of fantasy.
I would allow it to “work”, but with consequence.
”Yes, and” isn’t just good for improv.