Overview

COVID-19 antibody testing, also known as serology testing, is a blood test that's done to find out if you've had a past infection with SARS-CoV-2, the virus that causes coronavirus disease 2019 (COVID-19). An antibody test can't determine whether you're currently infected with the COVID-19 virus.

Antibodies are proteins produced by your immune system in response to an infection. Your immune system — which involves a complex network of cells, organs and tissues — identifies foreign substances in your body and helps fight infections and diseases. After infection with the COVID-19 virus, it can take two to three weeks to develop enough antibodies to be detected in an antibody test, so it's important that you're not tested too soon.

Antibodies may be detected in your blood for several months or more after you recover from COVID-19. Although these antibodies probably provide some immunity to the COVID-19 virus, there's currently not enough evidence to know how long the antibodies last or to what extent past infection with the virus helps protect you from getting another infection. Though rare, there are some confirmed and suspected cases of reinfection. Studies on COVID-19 antibodies as well as other components of the immune system are ongoing to learn more about immunity.

Antibody tests may detect certain types of antibodies related to the COVID-19 virus:

• Binding antibodies. These widely available antibody tests detect whether you've developed any antibodies in response to a COVID-19 infection. But they don't indicate how extensive or effective your immune response is.
• Neutralizing antibodies. Not yet widely available, a newer and more sensitive test detects a subgroup of antibodies that may inactivate the virus. This test can be done after you test positive for binding antibodies. It's another step toward finding out how effective your antibodies are in blocking the virus to help protect you from another COVID-19 infection.