SARS-CoV-2 Antibody Testing for Vaccinated People?
Although the FDA states that “antibody testing is not currently recommended to assess immunity after COVID-19 vaccination”, a significant chunk of the population wants to discover their antibody status to SARS-CoV-2, the virus that causes the illness COVID-19. The widely held public belief is that the presence of antibodies confers some resistance to illness, while the absence of antibodies means a person is vulnerable to infection and illness. However, the answer is not that simple.
The FDA’s explanationThe FDA explains that “results from currently authorized SARS-CoV-2 antibody tests should not be used to evaluate a person’s level of immunity or protection from COVID-19 at any time, and especially after the person received a COVID-19 vaccination.” In other words, antibody test results may only be used to inform the presence or absence of antibodies, and not to assume the level of immunity that equates to protection from illness.
Although the immune status of those with or without SARS-CoV-2 antibodies is officially uncertain at this time, there are a few things that we do know:
If you have SARS-CoV-2 antibodies:
Historically, medicine has assumed that the presence of antibodies to a pathogen equates to some level of protection from that pathogen. Repeated exposure to that pathogen (whether it be viral, bacterial, or other) would cause only mild or no illness. This long-held medical belief is the reason that adults can choose between receiving booster shots to certain pathogens such as measles, mumps, rubella, polio, etc, OR test their current antibody status to these pathogens. If there are significant levels of antibodies to the pathogens, then boosters aren’t required.
How is this different with SARS-CoV-2? Many experts believe that this traditionally held medical view also holds true for SARS-CoV-2: If you have antibodies, then you have protection from a significant illness from the virus. At the same time, many experts can’t state this as a fact for SARS-CoV-2, because the research to show that SARS-CoV-2 antibodies equate to immunity has not yet been completed. This virus just hasn’t been around long enough for long-term immunity studies to be finalized and published. As time marches on from the emergence of SARS-CoV-2, the research will continue, providing definitive answers to this question.
If you don’t have SARS-CoV-2 antibodies:
The scientific literature tells us that many people without detectable antibodies to the SARS-CoV-2 virus may still have immunity. In fact, multiple clinical studies have provided evidence that the majority of people exposed to SARS-CoV-2 but lacking antibodies have long-term immune cells known as cellular or memory cells. Long-term cellular immunity is not unique to SARS-CoV-2, as it is highly prevalent throughout the world of human pathogens.
Cellular immunity
In addition to antibodies, can we also measure cellular immunity? Currently, there is only one test with FDA EUA approval that can detect T cell memory, Adaptive Biotech’s “T-Detect”. There is also another cellular immunity testing company that is attempting to receive FDA EUA approval but that is currently only available RUO (research use only), Oxford Immunotec’s “T-Spot”. T-Spot has the added advantage of not just detecting cellular immunity to SARS-CoV-2, but also identifying whether someone has cellular immune cells that recognize the common human coronaviruses. This information is helpful because it can help researchers provide evidence to address a major question in our understanding of the SARS-CoV-2 pandemic: Can previous exposure to one or more of the common human coronaviruses lessen the severity of illness caused by SARS-CoV-2?
So, whether you have been vaccinated or whether you just want to know if you have antibodies to SARS-CoV-2, an antibody test can help provide one piece of the puzzle, but it’s not the full picture. If you choose to discover whether you have antibodies, it’s important to remember that not all antibody tests are created equal.
