When you do not have your dog’s vaccination records handy, it will be challenging to determine if he was vaccinated. Your vet could conduct a titer test. That is not done to confirm if your dog was vaccinated or not. Instead, a titer test helps to understand if a particular vaccine is ensuring complete protection for your dog. Your dog is immunized against a certain disease when the results are positive. A negative test result means he is yet to develop immunity. When your dog is not vaccinated, the titer test will be negative. But, sometimes, a fully-vaccinated canine may test negative and not develop immunity.