COVID-19 Antibody Testing Information

June 11, 2020

IMPORTANT: Regardless of whether you test positive or negative, antibody test results do not confirm whether or not you are able to spread the virus that causes COVID-19. Please continue to take all appropriate precautions to protect yourself and others.

What are antibodies?

Antibodies are proteins created by an individual’s immune system in response to an infection.  A positive antibody test informs a person that they have been previously exposed to an infection, and their immune system has responded by creating antibodies. Antibodies can help protect a person from the same infection. They can, in certain circumstances, provide immunity against a repeat infection. You can think of this as the immune system having a memory, and when the immune system notices the same type of infection trying to attack the body, the immune system releases antibodies to help fight the infection.

What is antibody testing for COVID-19?

An antibody test (also referred to as a serology test) is a blood test used to help determine if someone has been infected with SARS-CoV-2, the virus that causes COVID-19, in the past. This type of test cannot tell if you are currently sick with COVID-19.

What does it mean if I test POSITIVE for virus antibodies?

Per the Centers for Disease Control and Prevention (CDC):

  • A positive test result shows you may have antibodies from an infection with the virus that causes COVID-19, or possibly from an infection with a related virus from the same family of viruses (collectively called coronavirus), such as one that causes the common cold.
  • We do not know yet if having antibodies to the virus that causes COVID-19 can protect someone from getting infected again or, if they do, how long this protection might last.
  • You should continue to protect yourself and others since it is possible you could get infected with the virus again.
  • If you have no symptoms, you likely do not have an active infection, and no additional follow-up is needed.
    • If you work in a job where you wear personal protective equipment (PPE), continue wearing PPE.
  • If you have symptoms and meet other criteria for testing, you would need another type of test called a viral test. This test identifies the virus that causes COVID-19. An antibody (blood) test cannot tell if you are currently sick with COVID-19.
  • You might test positive for antibodies even if you never had symptoms of COVID-19. This can happen if you had an infection without symptoms.

What does it mean if I test NEGATIVE for virus antibodies?

  • This means you may not have had COVID-19 before.
  • Or you could still have a current infection.
    • The test may be negative because it typically takes 1 to 3 weeks after infection to develop 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 to others.
    • Some people may take even longer to develop antibodies, and some people may not develop antibodies at all.

Additional references:

https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/testing.html

https://www.cdc.gov/coronavirus/2019-ncov/testing/serology-overview.html