Playing with Google's cool new Book Ngram Viewer is fun. The data set is some 500 billion words culled from nearly 5.2 million digitized books in multiple languages starting in 1500. Read more about the project on the NYTimes.
I of course ran a quick diagnostic to see the relative frequency of zombies versus vampires. See graph below.
Vampires have enjoyed a longer history with a huge upswing in recent years but appear to have peaked. Meanwhile, zombies, true to form, are slowly but surely gaining ground, shambling upwards and onwards.