IME, dogs with intact immune systems, which is to say, our own personal dogs unless they are already ill, do not get kennel cough.
My own dogs have had it maybe 3x in the 10yrs. we've been rescuing and exposing them routinely to KC.
Dogs in shelters are susceptible to it, and usually get it, due to the stress of being in shelters.
From what I understand, the KC vaccine must be given a minimum of 3 days prior to exposure to actually work, so it was kind of pointless to give it the same day he was exposed
Also you're correct in that some dogs seemed to contract KC from the vaccine itself.