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.

-livescience.com

The good news is Costas Efthimiou has proven the impossibility of vampires. The bad news is he felt this was necessary.