1) I wanted share some data from a manuscript that just wen online at medrxiv.org/content/10.110…. This was spearheaded by the fantastic Dr. Ania Wajnberg in collaboration with many parts of the Mount Sinai Hospital and Icahn School of Medicine.
2) The data describes PCR and serology findings in the first 1343 plasma donors screened at Mount Sinai. Initially, there were two groups of donors: people who at some point had PCR confirmed COVID19 and people who had suspected COVID19 (but were never PCR confirmed).
3) The majority of these donors were mild cases. Now, almost all PCR-confirmed donors had antibodies, while the majority of the suspected COVID19 individuals did not. This tells us two things: a) the assay works and b) many people who think they had COVID19 might not have had it. 
4) When concentrating on the PCR confirmed donors we find that at first testing not all of them make antibodies, but many have high titers (in A). When we then recall people without/with low antibody titers for second test that vast majority of them becomes positive (shown in B).
5) Keep in mind that this ELISA assay that we use here was shown to correlate well with a neutralization assay (here: medrxiv.org/content/10.110…) basically suggesting that the vast majority make neutralizing antibodies, even if they were mild cases.
6) Now, this is expected. This looks pretty normal and is basically what we see for influenza. Sometime, somebody doesn't make antibodies (lack of seroconversion), but that is normal too. It is OK that this occurs, it happens for many other viruses at a low rate as well.
7) So, this is all good news. It still does not show that we are protected from reinfection, but it makes me feel pretty good. Now, Dr. Wajnberg found something in addition that is super interesting. Remember those reports of people testing positive again weeks after they.....
8)....recovered? Now, recently it was suggested that this is just viral fragments that are shed, not reinfection and not reactivation. Many of us have suspected this for a long time, and now we can maybe close that discussion. So, the donors were also tested by PCR when they....
9)....came in for their blood draw. And guess what? The latest PCR+ post recovery (not post-disease onset) we found so far was 28 days out. I find this extremely interesting. It is very likely that all this positivity you see below in red is genome, not infectious virus.
10) I need to go back to work, but stay tuned. I hope we will have more data for you soon. Lots of work, lots to learn. Stay home, stay safe!
