Elves can be vampires in D&D, it just depends on the edition I guess. I remember reading about a drow vampire in 3.5 ed book about dark elves, there is a vampiric sun elf Jander Sunstar + they exist in Ravenloft rulebooks: http://www.mojobob.com/roleplay/monstrousmanual/v/vampelf.html

I'm not very familiar with 5 ed, but I assume they didn't change this.