Vampires have been around since the beginning of recorded history, it isnt a trend. Twilight IS a trend, it just HAPPENS to be about vamps
This.
Same goes for "True Blood" and "The Vampire Diaries"... crap shows. These are trends.
Vampires and the legends surrounding them have been in every culture going back over thousands and thousands of years into human history.
Modern shows and books are the "fad", Vampires themselves are not a "fad". They are a deeply integrated part of Human culture.
Read a book on Anthropology and Human Culture/Mythology sometime.