All three of these supernatural beings are notorious for creating others of their kind via the respective paranormal viruses they carry. In a thunderous three way attack the vampire would have no effect because it’s supernatural vampire virus is only contained within it’s bloodstream. In order to create a Vampire one must be nearly drained of all human blood before ingesting vampire blood. So the battle is between the Werewolf, and the Zombie who do in fact transmit their extranormal viruses via saliva. The Werewolf, aka Lycanthrope, Virus is the strongest, and would eradicate the Zombification Virus. You would then transform into a Werewolf on the next full Moon. This is tons better than turning into a mindless cannibal composed of rotting flesh.
So if by some fluke you were simultaneously attacked by all three titans of terror, you would only become a Werewolf! Of course one would assume the vampire wouldn’t want the competition, and would proceed to eradicate the werewolf, and zombie. He or she might have to exert extra effort to take down the vampire depending on how long they lived, and what generation they are from. These factors determine a vampire’s strength. If the vampire had intentions to bring you across into the dark eternal shadows then the introduction of the vampire virus into your body would easily destroy the werewolf, and zombie virus. You would then become an immortal being who preys on humans for blood!