A COVID antibody test determines if you were previously infected with the virus (SARS-CoV-2) that causes COVID-19. Created by your immune system in response to SARS-CoV-2 infection, these antibodies can help protect you from developing COVID-19 if you are exposed to or infected with the coronavirus again (reinfection). A strong immune response to some viruses and other pathogens may protect you for life, but that is likely not the case with SARS-CoV-2.
Learn more about the COVID antibody test, including how it works, what your results mean, and the benefits of getting a COVID antibody test.
When you are infected with the virus (SARS-CoV-2) that causes COVID-19, your body’s immune system develops antibodies, which are special proteins that recognize the virus. Your immune system eventually clears the infection (in most cases of COVID-19), but some of the antibodies remain circulating in your blood. If you were exposed to the virus again, the so-called “memory” antibodies recognize it and help you fight it off, protecting you from getting sick.
A COVID-19 antibody test, or serology test is an immunoassay. It requires a blood draw. The test determines if your blood serum contains antibodies specific for SARS-CoV-2. The blood sample is mixed with the test material containing a SARS-CoV-2 protein—the “antigen.” If your sample contains SARS-CoV-2 antibodies, they will react with the viral antigen, generating a positive result.
It’s possible to test positive for COVID antibodies even if you don’t experience COVID-19 symptoms. That’s because antibodies take days or weeks to develop following exposure to the virus. So, you cannot use COVID antibody tests to diagnose a current COVID-19 infection.
SARS-CoV-2 is one virus strain in a family of viruses known as coronaviruses, some of which cause the common cold. If your antibody test is positive, it’s likely you were infected by SARS-CoV-2. However, it’s also possible to test positive for antibodies if you were infected with a different virus from that same family of coronaviruses. That’s because the antibody test is not 100% specific for SARS-CoV-2; antibodies your body has made to other coronaviruses may react with the test antigen. If you test positive, and you were never infected with SARS-CoV-2, your antibody test result is a false positive.
According to the U.S. Food and Drug Administration (FDA), a false positive is more likely when testing populations that do not have many COVID-19/SARS-CoV-2 infections. The FDA states antibody tests are a more reliable indicator of past COVID-19/SARS-CoV-2 infection when performed in populations with higher rates of COVID-19 infections.
Antibodies against SARS-CoV-2 can help you fight off infection and even help you from getting COVID-19 again, but this protection varies based on the disease and the individual person. Estimates of COVID-19 immunity range 3 to 6 months; studies continue to fully understand COVID-19 immunity and how long it lasts. Although rare, there have been confirmed and suspected cases of reinfection in COVID-19 patients. Scientists continue to study data related to reinfections to determine how they occur. So, having detectable SARS-CoV-2 antibodies, as indicated by a positive COVID-19 antibody test, is not a guarantee of immunity.
Because antibodies don’t form right away in response to an infection, you could receive a negative COVID antibody test if you were recently (or currently) infected and your immune system had not yet generated antibodies. Typically, it takes the immune system 1 to 3 weeks to start producing antibodies in response to SARS-CoV-2. For some people, it could take longer; or possibly, they may never develop measurable antibodies. If your COVID antibody test is negative, not only could you still get sick if you are exposed to COVID-19, but you also could unknowingly be contagious and spread the virus to others around you.
Unlike COVID-19 diagnostic testing, a COVID-19 antibody test requires a prescription from your doctor. COVID-19 antibody tests are not necessary for everyone, so talk with your doctor to discuss why you would need an antibody test. Check with your doctor or local or state health department to find a testing center near you, as the antibody tests are not as prevalent as COVID-19 diagnostic testing or vaccination sites.
Because there’s no guarantee of immunity with a positive COVID antibody test, it’s vital that you continue to take precautions to avoid contracting or spreading the COVID-19 virus. These include practicing social distance of at least 6 feet between others who don’t share your household, covering your nose and mouth with proper masking when in public settings, avoiding crowds and poorly ventilated indoor spaces, and frequently washing your hands with soap for at least 20 seconds each time.