Some humans got tired of being hunted by zampires and then being turned into zombies so that zampires could feast on fresh zombie meat. Some human scientists decided to even the score. They took advantage of one behavior that was never observed in zombies. They never ate one another. They only ate humans. And at that, they only ate healthy humans. So a group of human scientists decided to do a little experimentation of their own. They engineered a virus that would disrupt the the T-cell, zombie virus. In the ensuing chaos the doubly infected zombies would bite anything that moved.
The mad scientists were very proud of their laboratory shenanigans until they tried to enlist the aid of other normal humans to play this prank on the zampire. Ordinary humans pointed out what should have been painfully obvious. If the zombies ate one another, they would leave less food for the zampires. This would increase the raids of zampires on humans not decrease them.
The scientists went back to the drawing board. But before they did they hired a bounty hunter. The bounty hunter would do just about anything for money. The scientists paid the bounty hunter to bring back a zampire, in chains and alive. And they wanted a live zombie too. The scientists quickly decided to remove the immunity zampires had enjoyed from zombies attack. To zombies, zampires were infected with a fatal disease. The disease was a like a mutated version of the zombie virus. What was needed the scientists surmised was to infect all zombies everywhere with an overwhelming hunger to eat zampires and nothing else....