Test for Past Infection

Antibody blood tests, also called antibody tests, check your blood by looking for antibodies, which show if you had a previous infection with the virus. Depending on when someone was infected and the timing of the test, the test may not find antibodies in someone with a current COVID-19 infection. Antibody tests should not be used to diagnose someone as being currently sick with COVID-19. To see if you have a current infection, you need a viral test, which checks respiratory samples, such as a swab from inside your nose.

  • If you test positive:
    • A positive test result shows you have antibodies that likely resulted from an infection with SARS-CoV-2, or possibly a related coronavirus.
    • It's unclear if those antibodies can provide protection (immunity) against getting infected again. This means that we do not know at this time if antibodies make you immune to the virus.
    • If you have no symptoms, you likely do not have an active infection and no additional follow-up is needed.
    • If you have symptoms you would need another type of test called a nucleic acid test, or viral test. This test uses respiratory samples, such as a swab from inside your nose, to confirm COVID-19. An antibody test cannot tell if you are currently sick with COVID-19.
    • It's possible you might test positive for antibodies and you might not have or have ever had symptoms of COVID-19. This is known as having an asymptomatic infection, or an infection without symptoms.

  • If you test negative:
    • If you test negative for COVID-19 antibodies, you probably did not have a previous infection that has gotten better. However, you could have a current infection. It's possible you could still get sick if you have been exposed to the virus recently, since antibodies don't show up for 1 to 3 weeks after infection. This means you could still spread the virus.
    • Some people may take even longer to develop antibodies, and some people may not develop antibodies.
    • If you have symptoms you would need another type of test called a nucleic acid test, or viral test. This test uses respiratory samples, such as a swab from inside your nose, to confirm COVID-19. An antibody test cannot tell if you are currently sick with COVID-19.

  • These test results alone do not confirm if you are able to spread the virus that causes COVID-19. Know how to protect yourself and others.