I vaccinate mine, once every 3 yrs. we live in an area where we can meet a lot of wildlife and i take mine out a lot so i dont want to risk it.
There was a cd outbreak a couple of yrs back down south and 200 ferrets got wiped out most were vaccinated, the only ones that survived were vaccinated with Nobivac Dhppi. So its a bit hit and miss really. Mine also get vaccinated with nobivac.
It is entirely a personal thing i chose to because of where we live.