Antibody tests, like the name suggests, test for antibodies not viruses; so our COVID-19 Antibody tests don’t look for the presence of the coronavirus. Instead, they find the proteins, or antibodies, that our bodies’ immune systems makes in response to COVID-19.
Our COVID-19 Antibody tests look for two kinds of antibodies that our immune system produces in response to the coronavirus:
1. IgM antibodies
These are short-lived antibodies that our body makes when we are fighting off the COVID-19 infection. These antibodies normally appear from 7 day into fighting off the virus. If you test positive for this antibody, it means that you are a new COVID-19 infection, and you are contagious for the virus.
These antibodies only stay in your body for a short time and usually disappear a few weeks after your infection. That is why we can use this antibody to pick up if you may be infected with COVID-19. But that is also why it is recommended that should we pick up the IgM antibody, you should also use a PCR COVID (infection) test to confirm your infection.
2. IgG antibodies
The presence of IgG antibodies on your test can tell you if your immune system has ever had to fight off COVID-19. These antibodies usually appear in your blood 2 weeks after you recover from the virus.
IgG antibodies stay in your body a long time (sometimes for a lifetime) and help give you immunity against catching the virus again. If you test positive for these antibodies, not only will you know for certain that you had the virus, but you will also know that you have some protection against catching the virus again.