DHP is an annual vaccine for dogs. The D is for distemper, which is one of the most severe diseases in dogs. It's similar to measles for people. The H is for Hepatitis. This is uncommon in dogs because the vaccine is very successful. It is related to damage to the liver. The P actually stands for two things: Parainfluenza and Parvovirus. The first one is often seen when many dogs are housed together, like when they are being boarded. Some signs are coughing or the dog acting like it has something in its throat. The second P is a gastro-intestinal disease that was prevalent in the late 70's. The dog may vomit, have diarrhea, or get dehydrated.