Thanks for your replies, everyone.
To the folks who bring their pup out in public but would not allow strangers to pet the pup, what do you do when someone attempts to pet your pup without asking? Do you move the pup out of their reach and explain that you don't allow strangers to pet your unvaccinated pup?
It seems that there is no clear answer regarding whether strangers should be allowed to pet pups. There have obviously been studies recommending that pups be socialized extensively throughout the first four months by exposure to various people, sounds, and sights, but there is also a risk that the pup might catch a virus, even by being petted by a stranger. Sure, we can say the risk is low, but how do we know that unless we know where the person has just been? I would bet that most people do not verify that the stranger had not just touched another dog before being allowed to pet the pup. Furthermore, if the stranger is in a place that permits dogs (like a hardware store), chances are the person could have just pet another dog that could quite possibly have had a virus. You just never know.
Don't get me wrong, I am taking every precaution I can to protect my little guy, but there just seems to be conflicting information out there about the risks of contracting a virus. I mean, how far do you go to ensure your pup is safe? Do you take your shoes off before entering your home, especially if you are returning from a pet store? If so, do you require all of your guests to do the same until the pup is fully vaccinated? If you are walking down the street and pass a stray dog, do you turn in the other direction to protect your pup from the risk of contracting a virus that can be transmitted in the air? Like I mentioned above, do you make sure a stranger who wants to pet your dog did not recently touch another dog?
I would think most people do not take these precautions, and my question is whether you need to to protect your pup.