COVID-19 Antibody Test: About This Test

What is it?

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.

Why is it 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.

Antibody testing is important because:

• It could show who has already had COVID-19. These people might be safe to go back to work or school or to travel.
• It could show who hasn't had the infection. These people are still at risk. They need to keep taking steps to avoid the virus.
• It helps experts who are tracking COVID-19 learn more about the virus and how it spreads.

How do you prepare for the test?

You don't need to do anything to prepare for this test. But be sure to follow any instructions your health care provider gives you.

How is it 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 your results 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. 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. If this happens, you're still at risk for COVID-19.
• 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 probably haven't had COVID-19. But:

• You could get a 'false-negative' result. It takes a while after you're infected 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.