DETROIT – Local 4 News has received a number of questions about convalescent plasma donation, that’s plasma from people who have recovered from a coronavirus infection.
Some people also want to know if one can donate convalescent plasma after being vaccinated because they should have antibodies.
The answer is no and the reason is that after vaccination you only have antibodies to the spike protein. People who have survived an actual infection have antibodies that cover many more parts of the coronavirus.
Some viewers asked related questions.
One wrote, “I had my first COVID vaccine on Saturday and donated blood on Monday. I am told that the red cross screens for COVID antibodies. Will my recent vaccine impact that screening? If so, how?”
This is a really important question and can be broken down into parts. Yes, the Red Cross does screen for antibodies.
The test used for the screening is by Ortho Diagnostics and looks for antibodies to the all important spike protein (big spike on the diagrams).
That leads to the second part of the question, will a vaccine impact that screening?
The answer is yes. Both the Pfizer and Moderna vaccines cause you to produce antibodies to the spike protein and those will be found on the test used by the Red Cross.
But if you test positive for antibodies to the spike protein they do a second test. This one made by Roche and it looks for antibodies to a different coronavirus protein. It’s called the nucleocapsid, the small nubs inside the virus next to the RNA.
If your blood is positive for both spike and nucleocapsid antibodies it means you’ve been infected.
Also, if you are only positive for spike antibodies but not nucleocapsid antibodies then your antibodies are probably only from the vaccine.
That brings up another question from a different viewer who asked, “Is it recommended to get your antibodies checked after a certain amount of time to make sure you are still protected from the vaccination?”
The answer is no for several reasons. First off, not all available antibody tests look for antibodies to the spike protein which is what you make after vaccination.
Some antibody tests are expected to stay negative after you’re vaccinated.
Second, even if you did have a test for anti-spike antibodies and they’re positive, we don’t have enough data to know how that equates to protection from infection.
The only thing the presence of antibodies to the spike protein tells us at this point is whether someone has had a vaccine or been infected.