If ethically, you are deontological... telling the vampire they must die is self-negating; it is not something that can be willed, since you would not will that all creatures cease existing if any of them caused harm to others.
If you are utilitarian... telling the vampire they must die overlooks the possibility that their existence may lead to greater good.
If you are a virtues-based ethicist... telling the vampire they must be murderous toward themselves
If you are a pragmatic ethicisit... telling the vampire they must die is the same as saying a vampire must not be a vampire, which is a contradiction.
All of this is interesting, from a theory point of view, but, (in my view), there may be specific features of the dilemma which do not require a resort to this level of abstraction.
For example, I can conceive of examples where a person would sacrifice themselves for what they perceive as a "greater good". Or for their child. Or would make a small sacrifice locally for a perceived global good (such as my example of giving blood: It hurts, and I don't like doing it, but I find an overall good in giving blood, nevertheless.)
Also, (I think), you have to put more features in the Vampire's state: Actions do carry consequences to the state of the actor. Usually, a person cannot wholly forget or ignore the consequence of their actions. They don't act as simple logical machines, and must bear the memory of their actions. A vampire who kills their spouse because they could not otherwise survive might find their existence unbearable. On the other hand, a Vampire who must survive, and who drains the blood of an innocent, because that is necessary to prevent a greater harm (think Blade, in the first movie, where he drains blood from his companion close to the end), that could be justified. In my view, there are so many details of this to consider that they overwhelm an abstract method to telling correctness.
... which gets me back to a statement of "it depends".
One difference, I'm thinking, is whether there are scenarios where a person would (from their point of view) think of a good arising from their death, one which would cause a better result than if they survived. That does beg the question of whether that outlook is rational (or even sane), but that seems to be a key question to be answered.
To make a contrived example, we are on a spaceship, with barely enough food for us to reach a destination. Just so much food, water, air, and power to go around. There is an accident, and I have to enter the reaction chamber to fix it, but thereby expose myself to a large amount of radiation. Not enough to immediately kill me, but enough that I'll need more than my ration of supplied to survive to reach the destination. I could survive, but only by taking a larger share of rations, and most likely preventing another from reaching the destination. In this case, what should be done? Am I to be permitted to survive by causing another death? Would it matter what decisions were made before I volunteered to fix the reactor? What if I needed the resources of several people, not just of one, such that my survival would cause multiple deaths? What if I had key skills to help prevent an outbreak of a disease at our destination, and if I didn't reach the destination, thousands might die?
Thanks!
Tom