What happens if my dog gets vaccinated more than needed?

Like lets say if my dog got revaccinated with the same kind of vaccination that he recently got vaccinated for, would it be bad for his health? The problem is that someone abandoned the dog and doesnt care about him anymore and now im the one willing to take care of him but the previous owner wont tell me anything about the dog's vaccination history nor will the person tell me what vet the dog got taken care of. Should i immediately take the dog somewhere to get vaccinated just in case he needs it even though he might already be vaccinated recently?

it shouldnt cause any serious harm, and it would be better to be safe than sorry, take her to the vet and get her checked out, if she seems healthy maybe put off the vaccinations for a few weeks. ask your vet though, they will know best

Nothing will happen. The dog shelters are full of those kind of dogs and if they don't know the history they just start all over again with the immunizations and vaccinations, rabies too.

Just once probably won't hurt him, but I wouldn't do it all the time. I have read that dogs that are constantly over vaccinated have the tendency to grow lumps or warts (my toy poodle had one) for some reason. Chances are if the person who had the dog before you neglected him, he more than likely didn't bother taking the dog to the vet ever and is probably too ashamed to admit what an idiot he is.

he can start having seizures or start throwing up and having diharrea