I know everyone will get on me because I just flat out don't really think vaccinating does a whole heck of a lot of good for somethings, but so be it.
Anecdotal evidence for me, 3 of the 4 decent sized breeders of GSD's and Mal's where I get dogs from don NOT vaccinate for anything. They all used to at one point, but no longer do. I remember helping with a litter almost 10 years ago, it was their second litter of the year and half the litter came down with Parvo after vacination. This was the 2nd litter in a row that this happened. They never vaccinated again after that. I can't give an exact number of litters since then between gsd's and Mal's, but it's probably been on average 3-4 litters, sometimes more, per year so for 30 or 40 litters and not a single case again. Just lucky?
I have had at least 4 dogs come from those various kennels as pups and they went everywhere from the time they got here at a couple months old. Training fields, kennels, public parks, hardware stores, everywhere. I know that's a terribly small sample and not really relevant, but those were just mine. I know the owners, or at one time handlers of lots of those other dogs, and none ever got parvo.
I'm strange I guess and keep strange company
but most of the people i associate with do not vaccinate for anything other than rabies ever. Some will do one round of puppy shots and then none, but most do none. They actively look for breeders that do NOT give vaccinations to their puppies before they get them. My other breeder friends think they're nuts, but I gotta say they do have more longevity in their dogs overall and better health, but maybe that's just my biased eye, but every case of Parvo that i've known about has been from a puppy that has been vaccinated. I'm sure those working in vet offices have more exposure to those sorts of things than me, but my past experience really has me wondering why we even do them sometimes.