Apparently. That’s what happened to the Seditious Mind:
The great fortress of your thoughts has been breached, your unity broken. The network around and within you lies ruptured. You are cut out from the fabric, a hole in the whole.
This is the first choice you have ever been given.
So, the Taken Vex aren’t exactly ‘Vex,’ i.e., they’re no longer part of the Vex network. Taken Vex, in this case the Seditious Mind, go from part of the hivemind to an individual.
The Vex presumably did know about the Taken threat. The possibility of the Taken ‘infecting’ the Vex collective mind was why Paradox was such a crucial mission back in TTK. As Ikora says:
Ikora: If the Taken are here in the vault, they are at the heart of the Vex collective mind. Imagine the machine-planets of the Vex surging with Taken power. This must not be, Guardian.
This blight is probably why the Vex let Praedyth send out a message in the first place, in order to rid the Vault of the Taken:
Praedyth: [static] a message. The creatures will soon reach the heart of the vault. When [static] once they take the Vex, they’ll come for the Light.
Praedyth: [static] I don’t know why they’re letting me speak. Now, after so long.
Praedyth: Enslaved to a will they don’t understand. A will long dead here. Dead eons ago. But then, they won’t end, will they? Because you’re here.
Given that the act of Taking separates the Vex from the Collective, it’s probably not as simple as taking just a few Vex and letting the blight spread through the Network. That’s why the Taken had to (attempt to) infect the Vault, because it’s such a vital part of the collective mind. It’s entering spinfoil territory, but that may be why Quria didn’t introduce the Worms into its mind fluid- because it would spread to the whole of the network, as opposed to simply being Taken, which separates units from the network.