The problem is that your breeder started his vaccinations too early. Puppies should not get their first vaccination until they are 9-10 weeks old. Puppies get natural immunities from nursing their mother. These immunities remain in their systems for weeks after they are weaned. If the vaccinations are given too soon, these antibodies attack and kill the viruses in the vaccination leaving your puppy vulnerable to deadly viruses like parvo. It is called the 'window of susceptibility".
Window of susceptibility
The age at which puppies can effectively be immunized is proportional to the amount of antibody protection the puppy received from its mother. High levels of maternal antibodies present in the puppies' bloodstream will block the effectiveness of a vaccine. When the maternal antibodies drop to a low enough level in the puppy, immunization by a commercial vaccine will work.
The antibodies from the mother generally circulate in the newborn's blood for a number of weeks. There is a period of time from several days to several weeks in which the maternal antibodies are too low to provide protection against the disease, but too high to allow a vaccine to work. This period is called the window of susceptibility. This is the time when despite being vaccinated, a puppy or kitten can still contract the disease. Vaccination Recommendations for Puppies (Puppy Shots)
Dr. Jean Dodd's vaccination protocol has been adopted by 27 vet schools and is a good one to follow.
W Jean Dodds Vaccine Protocol VACCINATION PROTOCOLS