He did not originate that plot. Nor, as Darks mentioned, did his story involve vampires.
The reason to invoke a long-term plot is because vampires are long-"lived". They would need an adequate enemy.
I don't want to get into what I think the plot should be about. World domination seems obvious enough, perhaps the concealment of another method of achieving near-immortality. (Something evil and demonic, no doubt, especially if you want the vampires to be the relative "good guys.")
Now, that has possibilities! As well as a worthy adversary or two.
Ah... that's a good idea, something like "Interview with a Vampire" only with more eras , yes, it's an interesting backdrop - in the sense that the backdrop wouldn't really exist - differing periods.
Had an idea for a tale involving the eldest of vampires having to stave off the plans of what would be his 'son'.
Side effect is that humanity is saved.
There was some artifact that would have made a vampire near invincible.
Did I mention that The Eldest is the CEO of a corporation, that is under a threat of leveraged buyout by the same enemy mentioned above?
:Looks stern:
NNB are you a eatist? Just because their required form of nourishment is not universally accepted (and frankly rather gross) is no reason to condemn an entire race of intelligent beings as "evil".