Health Library

What Is Antibody Testing?

Antibodies (also called immunoglobulins) are proteins made by the immune system. Their job is to recognize and get rid of germs. They’re made after a person has been infected by a germ, or has been vaccinated against that germ. Usually, antibodies stay in our bodies in case we have to fight the same germ again.

Antibody testing lets doctors look for antibodies in blood.

How Is Antibody Testing for Coronavirus (COVID-19) Done?

An antibody blood test for coronavirus (COVID-19) uses a small blood sample. Sometimes the test can be done with a “fingerstick,” using a tiny needle (or lancet) to collect the blood from a fingertip.

Who Should Get an Antibody Test for Coronavirus (COVID-19)?

Experts are still studying how to use antibody testing during the pandemic. For now, it seems that only people participating in research studies should get these tests. Sometimes doctors will check for antibodies in a specific situation (such as when a child is in the hospital with MIS-C).

Antibody testing isn’t recommended for most people because:

• The tests can’t tell if a person is infected with coronavirus on the day they are tested.
• It isn’t clear how to interpret the results of an antibody test:
  • A “positive” result means the person has antibodies to the coronavirus. But doctors don’t yet know if this protects a person from being infected by the virus again. If it does, they don’t yet know how long that might last. So even someone whose test is positive should still do things to prevent infection like getting vaccinated, wearing a mask when recommended, and washing hands often.
  • A “negative” result means the test did not find antibodies in the person’s blood. But they still might be immune to the virus because other parts of the immune system also can offer protection from the virus.

So antibody test results aren’t a useful way to see if a person is immune to the virus, or to see if the vaccine is still working. When a test result is not helpful, there’s usually no reason to do it.

Talk to your doctor to see if antibody testing for coronavirus (COVID-19) is right for you or your children.

Where Can I Learn More About Coronavirus (COVID-19) and Antibody Testing?

Check the Centers for Disease Control and Prevention (CDC) and World Health Organization (WHO) websites for information about testing and other updates on coronavirus.