Why you should toss your COVID antibody test results in the trash - They're meaningless


Patients have been asking for COVID antibody tests. When asked why they give several reasons

  • I want to know if I've had COVID
  • I want to know if I'm immune
  • I want to know if I need a booster

The fact is that an antibody test can't really do any of these things for several reasons

  1. Antibodies are not our immune system. They are an important part of our immune system but they are only one part. Our immune system is incredibly complex with dozens of different cells playing critical roles and signaling each other with lots of chemical messengers. This complex choreography of immune cells and chemicals allows our bodies to react to lots of different pathogens. Antibodies are important but there are parts of our immune response that don't require antibodies at all and antibodies by themselves can't protect us unless it gets help from the rest of our immune system.
  2. We don't know what level of antibodies is necessary to provide good protection. There is a great deal of overlap between antibody levels in people who later get infected and those who don't.
  3. Antibody tests measure just one type of spike protein antibody. Infection and vaccination produce more than one type of spike protein antibody so a COVID antibody test does not even tell us a complete story of our antibody levels
  4. Related to the prior statement, different SARS-CoV2 viruses require different antibodies to neutralize them or different levels of the same antibody. For example the antibodies that patients formed to the original alpha variant of the virus offer almost no protection against the Omicron variant and the monoclonal antibody treatment that was designed for the earlier variants is ineffective on Omicron.

For all these reasons COVID antibody tests provide no useful information to the individual. They have some role for public health agencies who may want to use it to get an idea of the percentage of the population that is vaccinated or that had prior infection but even there its only a crude estimate.

Is there any danger to the test? Yes there is. Patients who have gotten this test have mistakenly assumed they had immunity from prior infection and that they don't need to get vaccinated, or that their previous vaccine is protecting them enough so they don't need a booster. None of those things are true and decisions based on that information can leave people and their families vulnerable. On the opposite end low antibody levels do not necessarily mean one is not immune. All antibody levels drop over time but the body retains the ability to produce them quickly if needed again in the future. In addition protection from viral infection relies heavily on our T-cell immune response which is not easily measured. Someone who has a “low” antibody level may incorrectly assume their vaccine did not work. In both cases patients may make incorrect assumptions that lead to flawed decisions that put themselves at risk.

The bottom line is that COVID antibody levels are not useful. They don't tell you if you had COVID, they don't tell you if you are immune, and they don't tell you if you need a booster. So please don't ask your doctor for an antibody level even if your friend's doctor did one for him.

Michael Melgar

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