An antibody test is a screening for things called antibodies in your blood. Your body makes these when it fights an infection, like COVID-19. The same thing happens when you get a vaccine, like a flu shot. That’s how you build immunity to a virus.

You may also hear it called a serology test.

The antibody test isn’t checking for the virus itself. Instead, it looks to see whether your immune system -- your body’s defense against illness -- has responded to the infection.