Antibody tests look for past infection
Antibody or serology tests look for antibodies in your blood to determine if you had a past infection with the virus that causes COVID-19.
- Antibodies are created by your body’s immune system soon after you have been infected or vaccinated.
- Antibodies help you fight off infections and can protect you from getting that disease again. How long this protection may last is different for each disease and each person.
A COVID-19 antibody test should not be used to diagnose a current infection with the virus. It can take up to 1 to 3 weeks after the infection for your body to make antibodies.
A positive COVID-19 antibody test means past infection
A positive antibody test is presumed to mean a person has been infected with the virus that causes COVID-19 at some point in the past. It does not mean they are currently infected.
You may test positive for antibodies even if you have never had symptoms of COVID-19. This can happen if you had an infection without symptoms, which is called an asymptomatic infection.
How long antibody protection lasts is uncertain
Having antibodies to the virus that causes COVID-19 may provide protection from getting infected with the virus again. But even if it does, we do not know how much protection the antibodies may provide or how long this protection may last.
You should continue to protect yourself and others since you could get infected with the virus again.
- Get a COVID-19 vaccine.
- Wash your hands often or use hand sanitizer.
- Stay away from others who are sick.
- If you have not been fully vaccinated, please wear a mask when around others.
A negative COVID-19 antibody test means no antibodies detected
A negative antibody tests means you may not have ever had COVID-19 infection. Or, you could have had a current infection or been recently infected and your body had not made antibodies at the time your blood was drawn for the test.
Read more about testing for past COVID-19 infections on the CDC website.