Antibody Tests Should Not Be Your Go-To For Checking COVID Immunity



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Testing your antibody levels to get a sense of your COVID-19 protection may be tempting, especially as you wait for a booster shot. But scientists say these widely available tests can’t tell you the full story, at least not yet.

Naveen Sharma/SOPA Images/LightRocket via Getty




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Naveen Sharma/SOPA Images/LightRocket via Getty


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If you do get an antibody test, can you learn anything from it?

Yes, as long as you don’t expect it to give you a straightforward answer for how well-protected you are from catching the virus. The FDA and the Centers for Disease Control and Prevention recommend against using antibody tests for this purpose, but it’s understandable that Americans are looking to these widely available tests for some indication of their immunity, especially given the growing concerns about declining efficacy of the mRNA vaccines over time. So what sort of legit information could you glean from the results?

Dr. Nicole Bouvier says it’s reasonable to look at how your results fit into the range of values of a particular test, to get a sense where you fall relative to others who’ve taken it. Lab companies may also be able to tell you the average level of antibodies of someone who had a coronavirus infection and recovered.

«That can give you a benchmark for the immune response to natural infection, and then you can sort of gauge your vaccine response against that,» says Bouvier, an associate professor of infectious diseases and microbiology at the Icahn School of Medicine at Mount Sinai.

The tests may give you numerical readings that indicate the level of antibodies in your blood that bind to specific SARS-CoV-2 proteins. «What we’re basically learning is that the higher your number is, the more likely you are to be protected,» Bouvier says, «and that you don’t actually need a super, super high number in order to be protected.» But this rule of thumb is based on large studies and doesn’t necessarily hold true on an individual level.


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The bottom line is that even doctors who are studying this topic don’t know what these antibody readings actually say about your immunity, says Haidar of the University of Pittsburgh Medical Center, who is running a study on coronavirus antibody response in immunocompromised individuals.

«We don’t know what the optimal antibody level is that correlates with protection,» he says.

For example, Haidar says it’s clear that immunocompromised patients may not have as robust an immune response to the vaccine, and that looking for the presence of antibody levels can hint at their level of protection. But even this can be misleading — because some research suggests that detectable antibodies from those patients still «may not be able to prevent infection as well as antibodies from people who are otherwise healthy.»

Haidar concedes that if someone has no detectable antibodies on the test, «even though they may have some protection from T cells — and we don’t have a full understanding of what this actually means — I can tell you that they are likely not as protected as someone who, let’s say, has an antibody level of 1,000.»

Only complicating the picture for consumers is that the tests on the market are not standardized. They can have varying degrees of sensitivity and look for different antibodies.

Some antibody tests sold commercially detect certain antibodies that are only generated in response to the actual virus. Getting a test that looks for these other antibodies (antibodies that target the nucleocapsid protein, for example) could lead someone who is vaccinated to get a negative result and falsely think they are not protected.

Despite all these caveats, the idea of a blood test that can eventually give consumers a reliable indication of their immunity is not far-fetched. «We have correlates of protection for other vaccine-preventable diseases like measles and hepatitis,» says Theel. «But we’re just not there yet with COVID.»

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