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.
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 that help stanch the flow from a cut. People deficient in one or more clotting factors have hemophilia and can face problems from a simple shaving cut. When making commercial quality anti-body rich products for things like diphtheria, rabies, snake bites and more, we let the plasma clot to form serum, which is then labeled antiserum for the particular entity. The less we transfer from donor to patient the better in most cases.
Before plasma is made available in a blood bank it’s also tested for things like hepatitis, AIDS virus and other pathogens. When preparing antiserum, we also calculate the titer or concentration of antibodies. We do this to standardize the dosage so that we know the concentration that produces a desired result (i.e. the patient getting better) and avoid giving a dose that is not sufficient.
Most antisera today contain animal antibodies because they are raised in large animals like horses that can donate gallons of plasma rather than pints that humans can. This might sound scary to some people but protein purification techniques that have been around for decades make these products safe.
Before human insulin could be made in a test tube, we used insulin from cow and pig pancreases (identical molecule) harvested at slaughterhouses. The insulin was purified of cow and pig proteins using the same basic purification techniques that could be used if we raised coronavirus antibodies in horses.
So, it seems the prudent approach to Covid-19 would be to make antiserum and to raise the antibodies in horses, not people. Antiserum would enable us to get the dosages right and to gather data on efficacy. It’s understandable that people wouldn’t want a loved one to be entered into a double-blind study in which they could get a placebo when antiserum holds so much promise. And a case can be made, given the years of experience we have in making antisera, that a double-blind study while remaining the gold standard, could be replaced in this case with a rigorous study of the effects of a coronavirus antiserum. I am sure that medical professionals will have varying opinions on this.
But now compare this with what the administration is doing. It’s using an emergency procedure that lacks good supporting information — I haven’t heard anyone talking about the varying titers of antibody from patient to patient for instance. They’re also not looking out at the future with any kind of plan to manufacture antibody therapies and make them ubiquitous and available to people in the early stages of the disease or even to people who are asymptomatic. The administration’s effort seems reckless and designed for speed and not necessarily accuracy and we really need accuracy at this point.
So to my trained eye, Trump’s announcement on convalescent plasma is not much more than a desperate showman trying to pull a rabbit out of his hat.