A positive antibody test indicates that you have antibodies in your blood that recognize and react with that specific pathogen, which is a strong indicator that these antibodies would likely provide immunity for some amount of time. In the case of COVID-19, it's difficult to know at this point how long, or even if, these antibodies can protect you from reinfection.
"The length of protection depends on a lot of factors, including how much antibody a person makes and whether the virus mutates," says Barber.
That said, antibody tests can be used not only to determine if a person has been infected with COVID-19, but also to gain a better understanding about how widespread COVID-19 is within a community. For instance, people who were infected with COVID-19 but experienced relatively mild symptoms will still test positive on an antibody test in the same way as someone with a very acute case.
"If antibody testing is conducted on a large scale, the results can be used to more accurately estimate how many people were exposed to the virus," says Barber. "Antibody tests will also likely play a large role in getting life back to normal. People with positive antibody tests will be able to show that they developed immunity to the virus, and thus are protected from reinfection — at least for an extended amount of time."
But Barber warns antibody test results should be taken with a grain of salt, as people who test positive may still have an active virus that they can spread to others. Therefore, the use of a test that tests for the presence of the actual virus paired with an antibody test for COVID-19 will likely give a more accurate picture of whether a person is safe to return to normal life.