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. Antibodies are proteins that help fight off infections. 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.
Antibody tests are available through healthcare providers and laboratories.
If you test positive or negative for COVID-19, no matter the type of test, you still should take preventive measures to protect yourself and others.
How to get an antibody test
Guidance on Interpreting COVID-19 Test Results pdf icon[610 KB]external icon: A guide for interpreting test results and determining what actions to take.
Check with your healthcare provider to see if they offer antibody tests.
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 and meet other guidelines for testing, 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 and meet other guidelines for testing, 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.
For healthcare professionals
For information on evaluating and testing, see recommendations for reporting, testing, and specimen collection
CDC’s work in antibody testing
CDC is evaluating commercial tests
CDC is evaluating the performance of commercially manufactured antibody tests in collaboration with other government agencies. FDA has authorized emergency use of several antibody tests.
For more information:
CDC is conducting serologic surveillance
CDC is looking at data from antibody tests to estimate the total number of people who have been infected with SARS-CoV-2 in the United States. CDC is also using antibody testing to learn more about how the body’s immune system responds to the virus and to explore how the virus spreads among people exposed to it. The information CDC is looking at comes from many groups, including blood donors and household contacts of people who had symptoms and were diagnosed with COVID-19.
CDC is supporting state, local, tribal and territorial laboratory capacity.