What You Need to Know About Antibody Tests

They might not be a true indicator of immunity

A healthcare worker takes a sample from a woman at a New York State Department of Health Covid-19 antibody testing center at Steve’s 9th Street Market in Brooklyn, New York on April 25, 2020. Photo: Michael Nagle/Xinhua News Agency/Getty Images

You’ve probably been hearing a lot about antibodies. These specialized proteins are made by the immune system when the body is infected with a new pathogen. Antibody testing for Covid-19 can give researchers a better picture of how many people have been exposed to the novel coronavirus and how it has spread.

As coronavirus antibody testing gets up and running across the United States, here’s what you should know.

What is an antibody test?

An antibody test is used to determine whether a person’s immune system has encountered a particular pathogen before. Antibodies are created in response to the presence of a specific pathogen and are programmed to recognize and attack them. They help the body fight off an immediate infection, but they also remain in the immune system for a while and provide protection against that pathogen upon future exposures. People who have been infected with SARS-CoV-2, the virus that causes Covid-19, are likely to have antibodies against it.

Most coronavirus antibody tests that are becoming available provide a positive or negative result, indicating whether or not you have SARS-CoV-2 antibodies. However, some antibody tests, like the one developed at the…