Kennel cough virus mutation

Recently when I took my old boy to the vets to have his annual health check up and vaccinations I was informed by the vet that in the last six months they had seen an increase in kennel cough amongst their knine clients.When I prodded abit futher the vet informed me that in actual fact the increase was amongst shock of all shocks vaccinated dogs.I asked the vet had the virus begun to mutate a resistance against the vaccine for kennel cough.She said that they were not sure but recommended that I didn't have my old boy done owing to the fact that he suffers from congestive heart failure and that he was so old.So does this worry you ?I know that we hear about resistant diseases in human treatments but I'd never heard of it in animal treatments before untill I'd prodded the vet futher.