According to Van Helsing, having one’s blood sucked by a vampire is enough to turn that person into a vampire when they die. This certainly seems to have been the case with Lucy; if true, all Lucy’s child victims will also one day become monsters. This is the traditional and folkloric view of the spread of vampirism: a form of supernatural disease.
However, if this were the case, then the vampire’s regular meals would soon have uncontrolled and devastating consequences. In 2006, a physics professor from the University of Central Florida argued that it is mathematically impossible for vampires to exist. Even if a vampire only needs to feed once a month (and Dracula certainly seems to crave blood more often), then if the first vampire appeared on January 1st 1600, it would only take two and a half years for the entire human population to be turned.
Apart from suggesting that physics professors have a little too much time on their hands, this argument also poses a huge problem for vampire fiction. The professor in question, however, has clearly not read much vampire literature, as there are two main ways in which this particular problem is resolved. One is the solution offered in Dracula, that killing a vampire will immediately remove the curse from all the people it has bitten: “but if she die in truth, then all cease; the tiny wounds of the throats disappear, and they go back to their plays” (p229). So killing Lucy saves the children, and killing Dracula saves anyone he might have fed upon. Presumably, had Lucy not already been dealt with, then killing Dracula would destroy Lucy and so also free the children. A neat solution; as long as there are a few vampire hunters around, the world will not be overrun with monsters.
Most other vampire fiction, however, takes a different route. In many, a vampire must share blood with his victim (i.e. he drinks a little of yours, you drink some of his) in order to make the change. This gives the vampire the choice of whether or not his dinner will become one of the Undead. This method is found in Anne Rice’s Vampire Chronicles, Buffy the Vampire Slayer, the Southern Vampires series (Sookie Stackhouse books/True Blood), and many more. Dracula performs a similar rite with one of his victims later on in Stoker's novel, in order to create a psychic link between them. In the Twilight series, it is the venom of a vampire's bite that creates new vampires. However, if the victim is drained before the venom can take effect, then the death is a normal one. Since most vampires drain all of their victims' blood, new vampires are rarely created.