Test for Past Infection (Antibody Test)
Updated June 30, 2020
Antibody tests check your blood by looking for antibodies, which may tell you if you had a past infection with the virus that causes COVID-19. Antibodies are proteins that help fight off infections and can provide protection against getting that disease again (immunity). Antibodies are disease specific. For example, measles antibodies will protect you from getting measles if you are exposed to it again, but they won’t protect you from getting mumps if you are exposed to mumps.
Except in instances in which viral testing is delayed, antibody tests should not be used to diagnose a current COVID-19 infection. An antibody test may not show if you have a current COVID-19 infection because it can take 1–3 weeks after infection for your body to make antibodies. To see if you are currently infected, you need a viral test. Viral tests identify the virus in samples from your respiratory system, such as a swab from the inside of your nose.
If you test positive or negative for COVID-19 on a viral or an antibody test, you still should take preventive measures to protect yourself and others.
We do not know yet if people who recover from COVID-19 can get infected again. Scientists are working to understand this.
How to get an antibody test
Guidance on Interpreting COVID-19 Test : A guide for understanding test results and determining what actions to take.
Antibody tests for COVID-19 are available through healthcare providers and laboratories. Check with your healthcare provider to see if they offer antibody tests and whether you should get one.
What do your results mean?
If you test positive
- A positive test result shows you may have antibodies from an infection with the virus that causes COVID-19. However, there is a chance a positive result means that you have antibodies from an infection with a virus from the same family of viruses (called coronaviruses), such as the one that causes the common cold.
- Having antibodies to the virus that causes COVID-19 may provide protection from getting infected with the virus again. If it does, we do not know how much protection the antibodies may provide or how long this protection may last.
- Talk with your healthcare provider about your test result and the type of test you took to understand what your result means. Your provider may suggest you take a second type of antibody test to see if the first test was accurate.
- You should continue to protect yourself and others since you could get infected with the virus again.
- If you work in a job where you wear personal protective equipment (PPE), continue wearing PPE.
- You may test positive for antibodies even if you have never had symptoms of COVID-19. This can happen if you had an infection without symptoms, which is called an asymptomatic infection.
If you test negative
- You may not have ever had COVID-19. Talk with your healthcare provider about your test result and the type of test you took to understand what your result means.
- You could still have a current infection.
- The test may be negative because it typically takes 1–3 weeks after infection for your body to make antibodies. It’s possible you could still get sick if you have been exposed to the virus recently. This means you could still spread the virus.
- Some people may take even longer to develop antibodies, and some people who are infected may not ever develop antibodies.
If you get symptoms after the antibody test, you might need another test called a viral test.
Regardless of whether you test positive or negative, the results do not confirm whether or not you are able to spread the virus that causes COVID-19. Until we know more, continue to take steps to protect yourself and others.
Learn more about using antibody tests to look for past infection.
For information on evaluating and testing for active infection, see recommendations for reporting, testing, and specimen collection.
For CDC interim guidance on antibody testing in clinical and public health settings, see Interim Guidelines for COVID-19 Antibody Testing.