Antibody Test for COVID-19
Overview
What is a COVID-19 antibody test?
An antibody test (also called a serology 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, it’s not yet known how the vaccine will affect the antibody test results.
Why is a COVID-19 antibody test done?
Most people don’t need this test. Antibody testing is mostly used to help track the virus, and the test is not commonly done in Alberta. These test results still mean that everyone must follow all public health measures to help stop the spread of COVID-19.
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:
- A positive result shows that you’ve already had COVID-19. But even if you have the antibody against SARS-CoV-2, you’re not considered immune to the virus. Keep doing things like wearing a mask, washing your hands often, and practising physical distancing.
- It could show who hasn't had COVID-19. Even though a negative result shows that you haven’t been infected, you’re still at risk. Keep taking steps to protect yourself from the virus.
- 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 will 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.
Credits
Adaptation Date: 3/21/2022
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
Adaptation Date: 3/21/2022
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
