You no doubt know that a diagnostic test for COVID-19 indicates whether or not you have been infected with the SARS-CoV-2 virus, the virus that leads to the disease known as COVID-19.
You also probably have heard that once you recover from COVID-19, your immune system more than likely has created antibodies in response to the infection. It can take several weeks after infection for antibodies to develop, so an antibody test can’t be used to determine if you have an active coronavirus infection. In other words, it can’t be used as a diagnostic test. Only PCR and antigen tests can diagnose an active SARS-CoV-2 virus infection (and they can do so whether or not you show COVID-19 symptoms).
This is so important we’re going to say it again
An antibody test does NOT show that you don’t have SARS-CoV-2!
In fact, because any antibodies that the test detects could have come from another type of coronavirus (such as those that cause the “regular” flu or the “common cold), an antibody test is not a 100 percent indication that you had the virus that causes COVID-19.
Benefits of an antibody qualitative test
A COVID-19 antibody test – also known as a serologic test – detects antibodies that are specific to SARS-CoV-2 in your blood. Most of the antibody tests used now detect IgG antibodies to a portion of the COVID virus known as the nucleocapsid, sometimes referred to as the N protein.
Having antibodies to the COVID-19 virus could protect people from getting re-infected with the virus, although it’s not an absolute guarantee. However, recent studies (as of August 2020) are indicating some signs of lasting immunity.
Caution, however, definitely is warranted
Getting a positive result on the SARS-CoV-2 antibody test in no way means you can discard your mask, go to a large party and mingle closely with old and new friends, etc. As mentioned above, the test could be indicating you have antibodies to another type of coronavirus. More importantly, while research is showing there may be some immunity bestowed upon you by the antibodies, as also mentioned above, it’s not definitive that they prevent re-infection. And, if they do, it’s still not known how long any immunity might last.
Remember: the viruses that cause the flu and colds are coronaviruses and immunity for these viruses last for only a few months or a year or so. Many experts, therefore, believe the coronavirus that causes COVID-19 could end up similar: providing some immunity for a few weeks or months.
Another important caveat: antibody tests shouldn’t be used to give people an “immunity pass,” because a) as far as we currently know immunity isn’t guaranteed and b) it could create a two-tiered workforce and even society. (The link explains this danger thoroughly.)
The-world-we-now-live-in benefits of antibody testing
Getting tested does have some real-life benefits. For one thing, it can tell people with more certainty if they had been infected with SARS-CoV-2 because some COVID-19 diagnostic tests return false negatives, even when people exhibit COVID-19 symptoms.
What’s more, it can help public health and medical professionals determine how prevalent the virus is in their area, allowing them to make better decisions about public health measures.
Antibody testing also can help COVID-19 researchers discover what type of immune response is most effective when an individual’s immune system fights the disease, which is a critical part of creating a vaccine.
Qualitative antibody testing also helps employers and their workers
While antibody testing should not be used in determining if someone should return to work – or not – it can provide your workers some peace of mind regarding the safety of your workplace.