Bigger issue is how long immunity lasts. If it only lasts a couple of months, then we're fucked until a vaccine is distributed. Nobody is going to stay locked down that long--odds are there will either be rolling lockdowns on smaller levels for 2-3 weeks every few months, or there will be light social distancing (but no actual lockdown) while recommending those most at risk stay inside. Countries simply can't stay locked down like they are now for 6+ months. Even 3 months is pushing it. Not just because of the economy, but because people are simply going to go insane after that point and not listen at all without the military going into the streets (and I don't foresee that going well with anyone).