I wouldn't take him out for walks where there is other dog traffic until after all of his shots are done. I'm no expert but I can say that my vet was very helpful with the timing of shots and restriction for my pup. Follow your vets guidelines for shots and don't take your pup anywhere but home until after the last shot is administered.
I did the same way with my dogs prior to our current puppy, but when I got the previous dogs(non-shepherds) I was also unaware of parvo risks. If I'm not mistaken it has really taken off in the last few years, there's been a lot of cases.
Do you have a fenced in yard? I would keep pup in the house and your own yard so that there's no risk of him getting it.