According to the University of Central Florida physics professor Costas Efthimiou's debunking logic: On Jan 1, 1600, the human population was 536,870,911. If the first vampire came into existence that day and bit one person a month, there would have been two vampires by Feb. 1, 1600. A month later there would have been four, and so on. In just two-and-a-half years the original human population would all have become vampires with nobody left to feed on.
This same University of Central Florida physics professor surmises that ghosts cannot exist since if they walked they would be beings of substance applying pressure on the floor; and this characteristic would coflict with their ability to walk through walls. But other physicists argue that ghosts are entirely possible according to quantum physics. Costas Efthimiou is oversimplifying and attempting to grab headlines at Halloween for his own 15 minutes of fame.