My puppies are 10 weeks and will have their second vaccine tomorrow. They won't go out and about until after the 3rd one at 13 weeks. We do as others have mentioned. We have lots of visitors here, from kids to older folks. They play all around in the house, hear the TV, washer/dryer, vacuum cleaner, normal human life. They are worked with individually each day on fun clicker play/training on how to stack, and basic obedience, attention, eye contact, recall.
They have a large outdoor play area that is on a solid surface so that I can keep it disinfected. I keep a wide variety of different toys for the puppies with them in this outdoor area. Things to chew, tug, chase, push, climb on, under and over. They also have a crate with a cushy bed in it where they nap during the day. I am in this area playing with the puppies several times each day, working on encouraging carrying, tugging, return with toys for play, recall, eye contact, etc.
My puppies do not touch grass or go out into public until 15 weeks. It has not been an issue for a number of puppies which I have raised in this manner.
At 15 weeks they will begin going out every single day to ride in the car, and visit a number of local businesses that have always welcomed me and my dogs to come in and play/work/socialize. They will also begin going to handling and training class one night a week to socialize in a dog-show-like environment.