Apr 15, 2020 10:00 AM

Health departments, labs, and hospitals across the country are rolling out antibody testing for COVID-19. Also called immunity testing or serological testing, antibody testing tells you if you had been infected in the past by the SARS-CoV-2 virus or COVID-19. That’s different from antigen testing, which determines whether you currently have the virus. Experts at University of Utah Health and ARUP Laboratories explain why this information is important.

What does antibody testing tell us?

Not everyone who has had COVID-19 realizes it. While hard to imagine, there are a number of reasons why that might be true. Some people may have experienced flu-like symptoms without knowing that they were caused by COVID-19. Others experience mild symptoms, and some people have no symptoms at all.

“Antibody testing will play an important role in the COVID-19 pandemic because it can tell us if a person has been exposed to SARS-CoV-2—even if that person never exhibited any symptoms or received a molecular diagnostic test,” says Julio Delgado, MD, ARUP Laboratories vice president, chief medical officer, and director of laboratories.

Why is it important to know who has had COVID-19?

Having antibodies against a virus signals that you have built an immunity against it. A positive antibody test for the new coronavirus could indicate that you’re less likely to be reinfected or to pass the virus to someone else. After all, this is what happens when we build immunity against the flu virus. However, COVID-19 is new and ongoing research studies will tell us for certain whether the same is true in this case.

If so, positive antibody tests could be used to decide who is allowed to return to work. This could be particularly important for health care workers and first responders who are at high risk for contracting the virus.

“A lot of people don’t know they had COVID-19 but they are immune,” says U of U Health virologist Vicente Planelles, PhD.

Antibody testing done on large numbers of people could be useful in a different way. It could track the spread of the virus throughout a population and determine which measures—such as social distancing or use of masks—work to slow the spread of the disease.

There is still a lot we don’t know about COVID-19.

While we’re learning more about COVID-19 every day, we still don't know all the answers. Long-term monitoring with antibody tests could tell us how long immunity will last. The test can also address another question: Why do some people have mild symptoms while others become seriously ill? 

Planelles anticipates using antibody tests to understand who is more equipped to defend themselves against COVID-19. Knowing this information could one day better identify and protect individuals who are more likely to develop complications from COVID-19.

“COVID-19 is brand new in the human population,” Planelles says, “and we still have a lot to learn about how to protect ourselves both as individuals and as a society.”

coronavirus covid-19 antibodies

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