Whether you vaccinate your dogs or not is your choice, but I think you probably need to speak with your vet about parvo risks in your specific area, as well as the prevalence of other deadly diseases, and then decide. Most likely they're not terribly prevalent because people vaccinate their dogs... For young puppies, diseases like parvo or distemper can be absolutely deadly. If you live in an area with wild animals, rabies and lepto are other risks that are deadly in adult dogs, let alone puppies (Rabies almost always, lepto occasionally, but more often in the babies or seniors). I think its probably luck that your seniors haven't picked anything up, and seeing as the usual round of vaccines (Distemper, rabies, etc.) last 3+ years, odds were in your favor.
Honestly, I'm not sure what raising a dog "naturally" means, but you can still raise a dog as green as you want while still having them protected against deadly diseases. Seriously, these diseases can be deadly to puppies and should not be messed around with. If you decide not to vaccinate, you have to keep that puppy away from areas where other unknown dogs have gone. So dog parks, pet stores, parks, pretty much anywhere public. Boarding the dog or taking him to classes would be out of the question since they typically require proof of vaccination.
Honestly, I'm not sure what raising a dog "naturally" means, but you can still raise a dog as green as you want while still having them protected against deadly diseases. Seriously, these diseases can be deadly to puppies and should not be messed around with. If you decide not to vaccinate, you have to keep that puppy away from areas where other unknown dogs have gone. So dog parks, pet stores, parks, pretty much anywhere public. Boarding the dog or taking him to classes would be out of the question since they typically require proof of vaccination.