Revaccinating your puppy and always making sure that your pup's vaccinations are up-to-date is one of the most important responsibilities of a puppy owner. Some puppies have a mild reaction when they are vaccinated. Tiredness, achy muscles, or a slight fever are some symptoms these puppies may experience. However, don't let that deter you! In a day or two, without treatment, things should be back to normal. It is very rare for pups to have a more serious reaction, such as breathing difficulties or swelling of the lips, eyes or neck. To keep your pup safe vaccinate him, but schedule the revaccination so you will be available to keep a close eye on your pup and watch for any symptoms after he has received the vaccine. If you have any concerns, contact your veterinarian immediately.