I don't think he's ever said this. As usual, providing a few citations we can follow would greatly help your case.

I thought he said the injured voice was due to worms eating his brain? It’s hard to keep up with such lunacy.

I don't think this is true? He has a neurological disease called Spasmodic dysphonia.

I can't find anything about this being related to a flu vaccine.

No, he claims that’s what caused it some years after being diagnosed.