My answer to your question doesn't cover the use against vampires, but there is a short story from the 1940s called Armageddon by Fredric Brown where it is used against a demon.
In the story a Tibetan prayer wheel stops which allows the devil who has been imprisoned in the body of a magician, to come back to life. But, of course, the magician was performing a show where a boy was asked up on the stage. When the devil starts to emerge, fire leaps from the fingertips of the magician/devil. The boy, seeing the fire, puts it out with the water from his squirt gun. The final part of the story is the father explaining to the mother why he punished the boy. They had apparently stopped at the church before going to the magic show. The father was mad because he realized there was no way for the boy to fil up his water pistols, except for having holy water from the font.