The test is similar to other blood tests you may have had before: A sample of blood is taken from the patient and is then analyzed to determine the presence of antibodies. Most tests will generally return results within a few days, but that may vary, as some tests can return results in a few hours.

If I have antibodies, I’m immune, right?

Not necessarily.

The antibody test does not test for immunity to Covid-19. There is no test yet that can tell if you are immune. It is simply too early to know if the presence of antibodies confers immunity, as this is a new virus, meaning we’ve never seen it before.

But experts generally agree that, based on experiences with other viruses, including SARS, the presence of antibodies most likely does confer some level of protection, though we don’t know to what extent or for how long.

“The difficult thing is we do not have clinical evidence yet of whether the presence of antibodies actually prevents the individual from getting the disease again,” Dr. Jhang said, adding, “I think most people believe that the presence of antibodies in most cases would confer some protection given our experience with other viruses.”

“But we really have to wait to see some evidence of that before we can be confident in being able to say that these antibodies can be protective,” he said.

If I get an antibody test, can it tell if I have the virus?

An antibody test is not the same thing as a diagnostic test for Covid-19, and it will not diagnose whether you currently have it.

Remember that antibodies take time to develop, so a lack of antibodies may just mean your body hasn’t had enough time to develop them postinfection.