Just a quick blurb today on an article that is in preprint and will come out shortly.  This is taken from the Johns Hopkins Covid site I had referenced before.  It is a good source of daily information on pandemic numbers and latest research.
ANTIBODY PRODUCTION IN COVID-19 SURVIVORS Researchers at The Rockefeller University published (preprint) data from a study of 149 COVID-19 patients to evaluate the presence of antibodies in blood serum after their recovery. Their analysis identified a broad scope of immune response among the participants, including the production of various types of antibodies. The researchers found that the majority of the COVID-19 patients did not produce the appropriate type or quantity of antibodies necessary to result in the “neutralizing activity” necessary to prevent SARS-CoV-2 infection, including 33% whose neutralizing activity was below the minimum detectable level. They did identify “remarkably high” neutralizing activity in 2 of the participants. The researchers were further able to identify and clone key neutralizing antibodies from these “‘elite’ responders,” and they are working to translate them into a potential COVID-19 treatment. 
This is a demonstration of what we have suspected all along.  Antibody production will not be an effective way to determine immunes.  Please don’t read this and be discouraged.  We know that the common strains of Corona Virus do not kill us.  In fact they cause relatively minor disease.  I feel this is because of a robust Memory T-cell immune response which we are currently unable to quantify.  What will take a long time to figure out is how do previously infected people respond when they are re-exposed.  This could mean that a reinfected person will not experience severe disease but will be able to transmit it to others.
I am diligently searching for ways to quantify T-cell function and the T-cell subsets I mentioned the other day are a relatively blunt tool for doing so.  Finally a shout out to our wonderful Manager/Personal Health Coordinator/ and all around Awesome Person Janette Fleites who having had Covid mounted an amazing antibody response and is an Elite Responder!
You Go Janette!
Warm Regards,