This film actually makes this connection more directly than any other vampire tale I've come across. It delves into the same territory that I tried to cover in my Eternal Hunger series (no doubt much more successfully).
In the film most humans have willingly been turned into vampires, and those who refused to give up their humanity are now hunted down for food. Blood farming corporations have sprung up to make profit from this natural resource. Due to the intense demand, the supply of blood is dwindling rapidly, and the vampires are frantically trying to come up with a blood substitute. Edward (Ethan Hawke) is a scientist working on the substitue for a major corporation, and he is also a vampire with a conscience. He refuses to drink the blood of humans and is disgusted by the way they are treated. We later learn he was turned against his will by his own brother.
It's interesting to read about the different interpretations people have of the film. One reviewer saw the way the humans are treated as a comment on the brutality of the capitalist system of food production,while another on Amazon claimed that blood actually symbolises oil: "Also, the political aspect is also a brilliant factor. Vampires being a metaphor for politics. Blood being a metaphor for OIL. This movie is very symbolic of how the government is greedy as hell when it comes to oil."
Both of these interpretations fit because I think it's a pretty all-encompassing critique of modern society and the greed that drives it.
The most powerful scenes in the movie for me are the one where the vampires turn on each other as the blood supply begins to run out. The poor are the first to suffer the effects of deprivation and they became public enemies to be rounded up by the state and killed. Those more fortunate have no sympathy for their fellow vamps and care only about protecting their own interests. They are completely oblivious to the fact that they will be next. The scenes with the military killing civilians and then turning on each other are spectacularly gruesome and effective.
Daybreakers takes the vampire metaphor and uses it to explore the true horrors lurking beneath the surface in modern society in a way that I think would make Bram Stoker proud. As the reviewer in the SMH said: "Daybreakers is a perfect panacea to audiences averse to the tweeny romanticisation of the undead by Twilight and its ilk."
Another blogger commented: "Someday Hollywood might make the vampire movie we really need, one in which the Dracula figure is a hedge fund manager or an oil company executive. This will be the fitting epigraph rolling across the screen in the opening credits:
Capital is dead labour, that, vampire-like, only lives by sucking living labour, and lives the more, the more labour it sucks.
–Karl Marx, Capital V. 1
I'll drink to that!