The risks that you are referring to are mostly associated with Parvovirus since that virus remains capable of infecting another dog for months after it is shed in an infected dog's feces. Public use areas such as parks, rest stops and any other high traffic dog areas are the greatest risk. Private outdoor areas are much less worry. You can't be sure your puppy is protected through vaccination until he has received a booster dose after 14 weeks of age. Vaccinations are usually repeated each 3 weeks until after 14-16 weeks. Take a look at the "vaccination" and ""parvovirus" videos.