I chose to assume it was not a re-infection and it just came back in a rare case, which is very possible. If not, we are dead and it's pointless planing around

I chose to assume it was not a re-infection and it just came back in a rare case, which is very possible. If not, we are dead and it's pointless planing around collapse of society. It makes much more sense to assume we have a solid ( IE at least a year in most cases) herd immunity. Planning around no herd immunity is like planning in depth around bankruptcy at round one funding.