Perhaps the vet didn't mention it as it isn't common in your part of the country? My vet in NY never mentioned it either. Not that Duncan had any of these symptoms then but I JUST found out that there is a vaccine too...
An internet search should give you some idea of how common it is where you live, as well as some other good info. Check that link Pam posted... ( I can't do a search or check for you for info as this computer is the pits)