It is possible to over-vaccinate your dog. The dangers of over-vaccination include the risk of serious side effects, the risk of immune system overstimulation, and even an increased risk of certain diseases. It is essential to consult with your veterinarian to determine the appropriate vaccine schedule for your dog based on its age and health history. If a particular vaccine is not indicated for your dog, then there is no benefit in giving it, and it can be harmful. Over-vaccination can also lead to the production of antibodies that can interfere with the effectiveness of certain vaccines, leading to mutations or even the creation of new viruses.