With the release of SARS-CoV2 booster vaccines and increasing questions regarding natural infection, there is renewed interest and confusion surrounding Covid-19 antibody testing. Both the research on Covid-19 antibodies and the tests continue to evolve rapidly.
Although immunity based on T and B cell memory certainly contributes durable protection against Covid-19 disease, there is evidence for a strong protective role of neutralizing serum antibodies in preventing infection and severe disease.
In one study that evaluated breakthrough infections in fully vaccinated health care workers, neutralizing antibody levels were significantly lower amongst those who had breakthrough infections compared to the uninfected control. Higher levels of neutralizing antibodies in those who did become infected also correlated with lower infectivity and symptom reports. Passive transfer of neutralizing antibodies has also been shown to prevent severe disease in multiple animal models as well as with available antibody treatments such as Regeneron.
One key question that has yet to be answered is at what antibody level can someone feel confident that they are protected from infection or severe disease. Although there is a general sense that "more is better," multiple studies have failed to define a clear cut-off point at which antibody levels can be considered protective. This lack of clarity reflects the complicated nature of our multi-layered immune system and the nuance required in assessing individual risk.
An antibody test may be a helpful piece of information in the broader assessments of someone's personalized Covid-19 risk assessment.
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Functional Medicine Labs for Covid-19 Antibody Testing
There are multiple types of Covid-19 antibody tests on the market today, and it can be difficult to know which test to order for which patient.
Rupa Health offers 3 Comprehensive Covid-19 antibody tests through USBioTek Laboratories and a Covid-19 Vaccine Immune Response Test by Elisa/ACT (discussed below).
All of these tests are slightly different, and understanding precisely what they are looking for can help practitioners choose the proper test for their patients' needs.
USBioTek uses the Elecsys test by Roche, which was one of the first antibody tests to receive FDA Emergency Use Authorization. This test uses enzyme-amplified chemiluminescence technology (CLA) designed to identify even small amounts of antibody proteins.
USBio Tek Covid IgG and IgM Antibody Panel:
- This test is best used for an unvaccinated individual who is trying to determine whether or not they have been exposed to the SARs-CoV-2 virus in the recent past.
This test provides both a qualitative and quantitative analysis of IgG and IgM antibodies for the SARs-CoV-2 virus. In the setting of a SARs-CoV-2 infection, IgM antibodies appear in the blood as early as 3-5 days after the onset of infection. IgG antibodies will start to appear roughly three weeks after the onset of infection.
Unfortunately, antibody tests can miss some past infections. One study found that approximately 5%-10% of individuals with documented Covid-19 infections did not develop any measurable IgG antibodies following an infection. There is also the issue of antibody count decreasing as time passes since the initial infection. We do not yet know exactly how long IgG antibodies are expected to last in response to a Covid-19 infection. One study found detectable antibody levels in some patients as far as 12 months out from infection. Still, the antibody levels dropped precipitously in the first six months, which could alter the reliability of test results. This test does not differentiate between antibodies created by a vaccine vs. an infection.
USBio Tek Covid Vaccination Response Screen
- This test is designed to assess the serologic vaccine response in an individual who has not been previously infected with Covid-19.
This test provides a qualitative and semi-quantitative evaluation of IgG and IgM antibodies to the SARS-CoV-2 spike protein receptor-binding domain.
Our current Covid-19 vaccines create antibodies directed at the spike protein. A natural Covid-19 infection will also generate antibodies to the spike protein.
USBio Tek Covid Immune Response Panel
- This test is a fantastic way to establish whether or not someone who has had a vaccine has also had exposure to the SARS-CoV-2 virus.
This test evaluates combined IgM and IgG antibodies to the SARS-CoV-2 nucleocapsid and the spike protein. Our current Covid-19 vaccines create antibodies directed at the spike protein of the virus.
Natural infection creates antibodies to multiple portions of the SARS-CoV-2 virus, including the nucleocapsid and the spike protein.
Since this test combines IgM and IgG antibodies, you would need to wait at least 15 days after a potential infection/exposure before drawing the blood to hit the 99% positive and negative predictive value associated with this test.
Functional Medicine Labs for Covid-19 Vaccine Immune Response
COVID Vax Panel by Elisa/ACT Biotechnologies
- This unique test looks at the immune system's response to components of the Covid Vaccines. This test can be helpful for patients who are concerned about delayed hypersensitivity to the PEG component of the vaccine.
- This test does not assess the risk of an immediate allergic reaction to any vaccine components.
The COVID Vax Panel by Elisa/ACT looks for lymphocyte activation and the associated immune response to PEG, a component of the current Covid Vaccines made by Pfizer and Moderna.
They use a technology called Lymphocyte Reactive Assay to see if exposing a sample of someone's lymphocytes to a chemical causes any cellular or biochemical changes in the lymphocyte.
Although this technology is relatively new within clinical medicine and is still undergoing evaluation regarding its clinical utility, early studies have shown reliability in determining whether or not a specific compound activates a lymphocyte on blind split samples.
Summary
Advising patients on their personal risk and their personalized care plan regarding COVID-19 is an active part of every practitioner's practice.
Understanding whether or not someone had a robust antibody response to a vaccine can provide valuable input.
The CDC has highlighted that we do not yet understand the "threshold of protection" value for serum antibodies and advocates for individualized risk assessments with a physician(CDC Statement).
Knowing how your patient responded to the vaccine and where their antibody levels are now can be valuable pieces of any patient's individualized risk assessment.
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