antibody test for covid-19

overview

what is a covid-19 antibody test?

an antibody test looks for antibodies in the blood. these are proteins that your immune system makes, usually after you're exposed to germs like viruses or bacteria or after you get a vaccine. antibodies work to fight illness.

a covid-19 antibody test looks for antibodies to sars-cov-2, the virus that causes covid-19. if you test positive for these antibodies, it could mean that you already had covid-19 or that you've been vaccinated for covid-19.

why is a covid-19 antibody test done?

this test can be used to diagnose a past infection with the virus that causes covid-19. many people who get covid-19 never have symptoms or have only mild ones. without antibody testing, these people might never know that they already had the virus. even if the test shows that you may have had covid-19, you need to keep taking steps to protect yourself and others from the virus. having covid-19 in the past may not prevent you from getting it again.

antibody testing is important because:

• it could show who has already had covid-19.
• it could show who hasn't had the infection.
• it helps experts who are tracking covid-19 learn more about the virus and how it spreads.

talk to your doctor about what the test results mean for you.

how is a covid-19 antibody test done?

this is a blood test. a health professional may prick your finger or use a needle to take a sample of blood from your arm.

what do the results of a covid-19 antibody test mean?

the result is either positive or negative.

a positive result means antibodies to sars-cov-2 were found. you probably already had covid-19 or had a covid-19 vaccine. but:

• you could get a "false-positive" result. the test might show that you have covid-19 antibodies when you don't. the test may find antibodies that formed in response to another type of coronavirus.
• it's not certain that having these antibodies will protect you from getting covid-19 again. and if it does, it's not clear how long the protection lasts.

a negative result means that these antibodies were not found.

• you could get a "false-negative" result. it takes a while after you're infected or vaccinated for your immune system to make antibodies.
• you could have a negative result but be infected now. you'd need a different test (viral test) to know if you have covid-19 now.