I’ve been advocating convalescent plasma since March. Now I cringe.

Back in March I wrote a piece advocating taking antibodies from patients recovering from Covid-19 and giving them to sick patients. The technique has been around in one form or another for over 100 years and the doctor who pioneered the treatment for diphtheria patients, Emil von Behring, won the first Nobel Prize in Medicine for it. At the time it seemed a safe emergency procedure that could be built out to be a real therapy, though not a cure.

This antiserum was raised in rabbits.

Plasma transfusion is a regular part of blood banking in the modern hospital. I know because I was once a blood banker. Just like any transfusion of blood products, you need to crossmatch donor product and recipient because the plasma also contains naturally occurring antibodies that can reject a transfusion and make a patient very ill or even kill.

Generally, if your blood type is B, for example, your donor should also be Type B. The wild card is Type O which accounts for about 45 percent of people. Type O can donate to Types A and B. A fourth category, Rh factor is listed as Plus or Minus (aka Positive and Negative) and generally a person with Rh Negative blood can donate to someone who is Rh Positive but not the reverse.

Plasma also contains other things like electrolytes, hormones, and other human proteins as well as clotting factors…