Não, no universo do filme eles não precisaram.
De este
...However, other rules such being repelled by crosses, holy water, or garlic does not seem to apply here, nor does the rule of vampires not entering a person's home without an invitation..
Também vale mencionar que o filme foi elogiado por abandonar muitos dos clichês de filmes de vampiros cansados.
Por exemplo
Scrapping many of the undead cliches -- including trading the whole blood-sucking thing for a much more frantic, and messy, brand of dining -- and aided by troublingly realistic special effects, Slade has crafted one hell of a monster movie.
That's saying a lot, since so many vampire films seem to end up treading the same old ground. But there are no garlic cloves here, no stakes in the heart, no evil-repelling crosses. Aside from vampires' aversion to sunlight and thirst for blood, Slade -- in a story based on the comic by Steve Niles and Ben Templesmith -- has pretty much rewritten the whole vampire rule book.