As more people recover from the novel coronavirus and seek to resume their normal activities, there’s been a lot of talk about testing for COVID-19 antibodies.

But what are antibody tests, exactly, and how do they differ from diagnostic tests for COVID-19? What do the results indicate for the people who take these tests? And what do they mean for how we should conduct ourselves during the COVID-19 pandemic?

Here are 5 things to know about the coronavirus antibody testing according to the MD Anderson Cancer Center.

What is antibody testing? and how is it different from diagnostic testing?

Diagnostic testing for COVID-19 involves looking to see whether an active virus is present — in this case, the coronavirus formally known as SARS-CoV-2. Laboratory technologists use a testing process to detect genetic material from the virus in samples swabbed from the very back of the nasal cavity. This testing is based on a common molecular testing technique: polymerase chain reaction (PCR).

By contrast, antibody testing (also called serology testing) is done with blood samples, because you’re looking for evidence of the body’s immune response to the virus.

After your body is exposed to a foreign pathogen, your white blood cells start to learn about it and make antibodies to neutralize it. So, when an antibody test comes back positive for this coronavirus, it means 1) you were exposed to SARS-CoV2 at some point in the past and 2) your immune system was robust enough to launch an antibody-forming immune response.

How long does it usually take people to generate these antibodies?

There are limited data related to antibodies against SARS-CoV2. Some reports suggest most healthy people start making antibodies 11 to 14 days after symptoms first appear.

But there are also other variables to consider, such as malnourishment, having cancer or another chronic health condition, or taking immune suppressing drugs. All of these can affect people’s ability to make antibodies.

What does a positive antibody test result mean for someone in terms of immunity?

The short answer is we don’t know.

It may mean someone has full immunity or partial immunity or no immunity at all. Some antibodies decrease over time, so you might be immune for six months to a year, and then maybe not at all later on. Or, it might be like a tetanus immunization, where if you get it once, you’re most likely immune the rest of your life. There’s just no way to give definitive answers right now.