The anti-body tests will establish that one way or the other...should not have long to wait....
https://www.livescience.com/colorado-ski-town-coronavirus-antibody-testing.html
For those of us paying attention, it's pretty clear that one of they key elements will be some kind of random statistical sampling process to determine who had it, who has it, and who is still clear. Without that key information, we're blind as bats (pun intended); I don't think anyone has enjoyed this experience of the speculative unknown.
Once armed with that type of real time data, then the whole logistical process of deployment, resource allocation, supply lines, vaccine R&D, etc immediately come into play. No wants another shot gun approach to shutting down the entire country.