I would tend to take issue with Vets who believe it's useless to give antibiotics for Kennel Cough.

True Kennel cough is usually a combination of an initial Virus belonging to the parainfluenza, or adenovirus strains. What quickly follows that is a secondary infection caused by Bordetella bacteria. The Kennel Cough nasal vaccine is directed against all 3 infectious agents. Although the immunity conferred by the vaccine lasts about 1 yr.

In general a virus is dependent on a health host for successful replication. A bacteria is dependent on a sickly host. Thus the virus infects the healthy host, and once run down from the viral infection the bacterial infection takes off. In the case of Kennel Cough it's a guessing game as to how weakened the immune system has become due to the viral infection. If not much then yes the dog should be able to combat any subsequent Bordetella that try to take advantage of the situation. On the other hand if the viral infection really ran down the dog or in an immature or compromised immune system then the Bordetella part of the illness can be prolonged. In puppies the subsequent Bordetella infection can in concert with other bacteria progress to serious pneumonia.

Ironically some Vets argue that using antibiotics too soon may encourage antibiotic resistance hampering efforts to combat the pneumonia later if it should develop. Logically this doesn't make sense since Clavamox has a low profile for resistance, Baytril even lower (i.e. Baytril should not be used in puppies), and Zithromax is the current wonder antibiotic with nearly no resistance. Why wait for complictions to treat? Also most antibiotic resistance in bacteria is pre-existing. Probably their concerns are valid if they typically only prescribe a wide spectrum antibiotic such as Doxycycline. Exit antibiotics mode...

In general although antibiotics will have no effect on the initial viral infection, they will help the dog avoid complications of pneumonia, and allow it to recover more quickly. There is really no reason not to treat with antibiotics.