Originally Posted by Skeptic Ginger
Since there are already over 1 million recovered patients
in the USA alone, a trial should be relatively easy to conduct.
Recruit X number of recovered patients and an equal number of people who haven't had it yet to be a control group.
Exactly how large X needs to be should be a matter for the statistics people to figure out. But the larger, the better.
For this trial you don't need to administer any drugs or placebos, you just need people to agree to be tested every few weeks or so.
Make the control group as close as possible demographically and geographically as the study group. Over time, presumably, some fraction of the control group will test positive. If nobody from the study group, or a significantly smaller fraction than the control group tests positive, you know that they have some immunity or at least resistance to reinfection.