One key theme is the battle between good and evil. The vampire represents pure evil, preying on the innocent. Another is the theme of sexuality, often hinted at through the vampire's allure. Also, there is the idea of the supernatural invading the normal world.
In Bram Stoker's vampire novel, the themes are complex and intertwined. There is the theme of isolation. The vampire is an isolated being, and those it attacks also become isolated from society as they transform. The concept of the other is strong too. The vampire is the 'other' that the human characters have to face. Moreover, the theme of faith plays a role. The characters' religious beliefs are tested in the face of this unholy creature.