Kennel Cough is a respiratory infection and is passed in bodily fluids from dog to dog - vaccinated dogs have the antibodies to keep the infection at bay and have no symptoms but it is alive in their bodies if they have been exposed to it. There are many strains so vaccination may not cover your dog. A vaccinated dog that has been exposed may carry the infection and lick, snuffle or even normally greet or play with other dogs and so pass it on.