Some companies and states are starting to use antibody testing to consider some individuals "immune" from further Covid-19 infection. Unfortunately, no antibody test out of the 150(!) that are trying to become used have ever been approved by the FDA. Some received "EUA" designation or "Emergency use authorization" but this does NOT mean it was ever validated or sanctioned by the FDA as safe or accurate. Some authorities even go so far as to say that some of the antibody tests are "fraudulent." Recently, we were approached by an antibody testing company to use their product for Cleared4Work and backed away when I asked to see any data on its accuracy (I would have taken internal data, not even done by the FDA). I got nothing.
No accurate antibody data means a well-researched symptom monitor accompanied by real-time contact tracing and a comprehensive business strategy will be the only way to minimize Covid-19 outbreaks in the workplace for now and the foreseeable future. A great discussion of this issue is in the article from Politico referenced below.
April 29, 2020