Lol
I start taking them out to quiet parks for a walk when they are 18 weeks.
Mine gets their last boosters at 16 weeks, then I allow 2 weeks for the vaccinations to be fully effective.
Mine get carried into pet stores or around town before then, I just don't put them on the ground where there is a risk of catching something.
It's mostly just for socializing early on, not actual exercise.
I spent about an hour at a park in the middle of town today with my pup (now 19 weeks) we just walked around the border then sat on the grass and watched people going past.