In a scenario severe enough you're trying to make your own antibiotics, you can assume hospitals aren't functioning, which means civil society is gone.
You can't assume the government is gone, BTW: Every power vacuum will get filled, one way or the other, and there are plenty of unrecognized governments which are as governmental as they need to be to enforce their idea of order in a defined region.
Therefore... you, the prepper who was responsible enough to squirrel away tools and knowledge and supplies, are a target. If the government is trying to rebuild, it's going to be seizing supplies and, possibly, conscripting anyone capable of using those supplies who didn't have the good sense to leave when the getting was good. If the government isn't trying to rebuild... well, since when have gangs not looted anyone with stuff worth having?
It comes down to a survivalist fantasy, which amounts to one person, one family, one karass, against the world. A small, intimate group, as opposed to the granfalloon with guns which is called a military. Well... when a small group goes up against a big group, the small group is almost always fated to lose.
"Stable ownership is the gift of social law, and is given late in the progress of society." --Thomas Jefferson to Isaac McPherson, 1813. ME 13:333