The canine distemper vaccine, abbreviated as DA2PP, is a combination vaccine that protects against four deadly diseases, one of which is distemper. The "D" in DA2PP stands for distemper, which is a highly contagious and often fatal viral disease that affects the respiratory, gastrointestinal, nervous system, and other organs of dogs. The vaccine is recommended for use in healthy dogs as an aid in the prevention of disease caused by canine distemper virus, adenovirus type 1 (hepatitis), adenovirus type 2 (respiratory disease), canine parainfluenza virus, and canine parvovirus. Puppies can receive the distemper vaccine at six weeks old and then every three to four weeks until 16 weeks old, and immunity may last for three years or more. It is important to follow your veterinarians recommendations and complete the proper dose of the distemper vaccine to ensure maximum protection.