I also agree with JM...
and I would think that aside from being ineffective, it could weaken the immune system, causing the dog to be more susceptible to infection.
I don't mind URIs too much... I've had a few dogs catch them over the years (while being vaccinated), not a major issue in a healthy dog, and we've never needed to get a vet appointment for them. They've been exposed probably close to half a dozen+ times in the last few years at events, the park, daycare, etc...