my most stable-temperament dog was extremely well socialized- the foster parents took the entire litter of 13 puppies to malls, schools, and stores from age 4 weeks on as a way to promote their rescue. The pups saw everything under the sun while in the comfort of their litter and with their mother. When I got her at age 8 weeks, I continued the “take her everywhere” trend. She passed her therapy dog certification with flying colors with no effort at all on my part. My least stable temperament dog was isolated by the breeder until age 12 weeks. He never left the premises until I picked him up. Even by that tender age the lack of exposure to the world had left its mark.
You should read “The breeders guide to raising superstar dogs” by Jerry Hope. It talks about how the early environment of a puppy can be manipulated to profoundly affect how the dog turns out.
The major cause of dog deaths in our society is behavioral problems. Worrying about a minor risk of parvo or distemper is very unwarranted in our world. You need to worry about your dog’s temperament a lot more than about a tiny risk of parvo.