Discussing antibody tests and when to expect a positive result!
When infected naturally with SARS-CoV-2, your body is exposed to all the viral proteins and will generally make antibodies against the two most immunogenic proteins – the Spike (S) protein and the Nucleocapsid (N) protein. In this case, any serology (antibody) test designed to detect anti-S-antibodies or anti-N-antibodies should be positive (if taken within a good window after infection).
When vaccinated (with any currently EUA approved vaccine) your body is only exposed to the Spike protein and will therefore only make anti-S-antibodies. In this case, any antibody test designed to detect anti-S-antibodies should be positive BUT any test designed to detect anti-N-antibodies should be negative (again if taken with enough time for antibodies to develop).
I have seen some people confused when a vaccinated person takes an antibody test and receives a negative result. It is very likely, in this case, that the vaccinated person took an antibody test looking for anti-N-antibodies. And the vaccine doesn’t expose you to the N protein… so the test, in this case, should be negative.
Check the FDA website for a very long list of EUA approved serology (antibody) tests for SARS-CoV-2 – each test indicates if it is detecting anti-S-antibodies, anti-N antibodies, or both! Source on slide 4.
It is important to understand what test if being given to you so you can properly interpret the results.
Topic inspired by one of @christinaaaaaaanp ‘s most recent posts. Go check it out!
Posted on Instagram on March 3, 2021.