Well, WCVs like to use cats paws against their foes. If they control an entire hospital, and the players are inside, that's a lot of power they can wield against them.
I mean it's really not the vampires fault that the characters breached a quarantined area and now have to be kept for 4 weeks. And it clearly isn't the vampires fault that the medicine was laced with tranquilizers. Or that the tranquilized characters were transported to a private care facility and the paperwork got lost. Honestly, Officer. If only I'd known, I could have helped them.
Sure, the players can bash their way through mortals, injuring or even killing some of them, but that should be a moral problem for most players. If the players get away, they will be hunted by people in hazmat suits, because they carry a dangerous disease which is not only highly contagious, but also makes them violent and delusional, so they will probably not hesitate to use lethal force.
And all that will take the WCV is one phone call.