Can the coronavirus antibody test measure your protection against Covid-19?

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If you’re looking for a single magic number to say if you can be more lax about taking precautions against Covid-19, I’m sorry but the level of antibodies in your blood won’t provide it. Antibodies aren’t like One Direction shirts. Having more shouldn’t necessarily make you more comfortable. It is not so easy.

The role of antibody testing against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has evolved since Covid-19 vaccines became widely available. In 2020, such a test was the only way to tell if you had protection against Covid-19. But that hasn’t been the case in the US since December 2020, when vaccination began. That hasn’t stopped some people from continuing to make misleading claims about what such tests can tell you. After all, there are, surprise surprise, people out there trying to make money off the pandemic and, in some cases, trying to scam you in any way they can. As they say, grifters will grift. So you have to be careful about what you hear and do.

Of course, just because someone offers an antibody test doesn’t mean it’s legitimate. So before you have such a test done for any reason, first make sure that the test has at least an Emergency Use Authorization (EUA) from the US Food and Drug Administration (FDA). Check and make sure the test is on that Performance list of FDA’s EEA-approved serological tests. For example, something called the Vegan Hot Dog Awesomesauce Glow Up Antibody Test would not be on this list. Also, ensure that the spelling of the test name matches that listed on the FDA website. For example, the “A butt” test is not the same as an “Abbott” test.

These tests are not called serological tests because they have anything to do with the actor in the film Scott pilgrim vs the world. Otherwise they would have been called Michael Cera tests. Instead, in this case, serology refers to what’s in your blood serum, the liquid part of your blood. These are tests that look for antibodies in your blood serum, unlike other body fluids. So if someone asks about your urine or semen, you may be getting the wrong type of test. There are two general types of SARS-CoV-2 serological antibody tests: (1) qualitative, which simply tells you if antibodies are present in your blood, and (2) quantitative, which indicates a level of antibodies in your blood.

Even if you can get a legitimate SARS-CoV-2 antibody test, that doesn’t mean you should necessarily proceed with the test. Sure, there probably won’t be any significant physical harm from getting an antibody test like this. It’s not like someone implants a microchip or magnets in your body when they draw your blood for the serology test, is it? The big question, however, is whether the test tells you anything useful at all. After all, the words “blood test” and “lots of fun” usually don’t go together.

Remember that antibody tests will not tell you if you have Covid-19 or are contagious:

Instead, you need to get a SARS-CoV-2 antigen or molecular test to check for the presence of the virus. Antibody tests can only tell you if you’ve ever been exposed to the virus or the spike protein, or both. It can give a sense of whether you’ve had some sort of immune response to the virus. Even so, the Centers for Disease Control and Prevention (CDC) website. It specifically states: “Antibody testing is not currently recommended to assess immunity to SARS-CoV-2 following Covid-19 vaccination, to assess the need for vaccination in an unvaccinated person, or to assess the need for quarantine after a establish close contact with someone who has Covid-19.” In other words, the CDC says you should not rely on antibody testing to assess your level of protection against Covid-19.

Why might such tests be unreliable? First off, antibodies are by no means the only way your immune system can protect you from Covid-19. Focusing on antibodies would be like focusing on just one player in defense on a soccer team, or just the violins in an orchestra, or just Niall Horan in One Direction. Your B lymphocytes (white blood cells) can produce antibodies that can block and inactivate the virus. This is just one aspect of your immune response. Your B cells, T cells, and other other cells can also do a whole host of other things, like secrete chemicals that make it harder for the virus to do its damage, or eat away at virus-infected cells. The mere presence of antibodies does not necessarily mean that all other types of immune protection are working and vice versa.

Second, it is not clear what level of antibodies is sufficient for adequate protection, whatever “adequate protection” means. Like the number of garden gnomes in your front yard, higher antibody levels can be better. A study published back in October 2021 in the New England Journal of Medicine showed that healthcare workers in Israel with higher levels of antibodies tended to have lower rates of breakthrough infections with Covid-19. However, unlike the underwear you wear, there is no magic threshold beyond which you are adequately protected.

Third, over time, your immune system can make different types of antibodies against the SARS-CoV-2 spike protein. If you remember, spike protein is what litters the surface of the Covid-19 coronavirus, making it look like the end of one of those BDSM maces, like the ones you keep tucked under your bed. Shortly after encountering either the spike protein from the vaccine or the whole virus from a natural infection, your B cells start producing IgM. In this case, Ig stands for “immunoglobulin,” another name for antibodies, and not for “Instagram” or “I think.”

IgM secretion is part of the early immune response, with IgM levels rising rapidly within the first few days and peaking fairly early before falling. In comparison, levels of IgG, or immunoglobulin G, which are also produced by B cells, rise more slowly and may peak several weeks after the spike proteins or virus are gone from your body. IgGs help with longer-term protection. IgG levels can remain elevated for extended periods (weeks to months) long after IgM levels have fallen.

The following video from Beckman Coulter Diagnostics shows how these different antibody levels rise and fall over time:

The problem is that a given antibody test may not distinguish between these different types of antibodies and therefore may not give you a better sense of their status.

Finally, the number of antibodies generated by either Covid-19 or the Covid-19 vaccine can vary from person to person. In case you haven’t figured it out yet, people aren’t exactly the same. For example, what works for Brad Pitt may not work for you. So don’t compare your antibody levels to those of your significant other, or your friends, or your bitter rival, or a stranger at the donut shop.

That being said, antibody testing isn’t entirely useless. They can still provide useful information depending on the circumstances. Antibody levels can, for example, provide information about whether you have been vaccinated against Covid-19. Antibodies against the S protein may be present if you have either been vaccinated or previously infected. Antibodies against N protein may be present if you have previously been infected. Of course, in most cases there are other ways to determine this, e.g. B. To remember that you have been vaccinated. Normally you wouldn’t have let a bunch of ninjas inoculate you in the middle of the night in your sleep. And vaccination while intoxicated is discouraged.

However, if you have questions about storing and administering the vaccine, you should check that you have actually been vaccinated. Or maybe your immune system is weaker because of the medications you are taking, other medical conditions you may have, or your age. An antibody test can help check if your immune system has responded to the vaccine.

Such blood serologies may also have broader public health applications. Scientists and public health officials can use this information to track what percentage of the population may have already been exposed to SARS-CoV-2, allowing them to make recommendations on when to relax or tighten certain Covid-19 precautions. That would depend on people’s test results being made available to health officials and scientists. It also depends on whether politicians actually listen to what scientists and health officials are saying. Both cannot be the case.

All in all, you shouldn’t be using antibody tests to decide what to do about face mask wearing, quarantine, other social distancing measures and ventilation, or whether to get vaccinated. Instead, try to take at least three types of Covid-19 precautions and follow public health recommendations at all times, no matter what your antibody levels are. Natural infection is not a substitute for vaccination. As I previously covered forbesStudies have shown that vaccination may offer much better protection than natural infection, especially since natural infection can vary so much in its course and severity and the resulting immune response.

As with many things in life, your immune protection against Covid-19 is complex. A single number can rarely tell you enough to make a decision…unless it’s something like the number of groundhogs in your bed.

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