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  • Carmen Zajicek

Antibody Testing After the COVID-19 Vaccine

With the pandemic taking over the world and impacting every country, all of last year was spent under lockdown and went by while social distancing. The virus has been quite severe, infecting millions and resulting in around 3.494 million deaths.


Even though general safety measures have been published and increased awareness of these, it has been challenging to curb the spread of this virus. The only plausible solution to the pandemic has been to develop a vaccine. With Pfizer/BioNtech being the first vaccine to be rolled out in the US, several nations such as the UK and China have started to develop their vaccine. With many more vaccines coming up in the near future, an important question on everyone’s mind is whether the vaccines are effective in reducing the risk of infection and if an antibody test is needed to measure this.


How Do Vaccines Work?


It is essential to understand how infections affect your body before explaining what a vaccine can do. When your body encounters an infection, the defensive white blood cells in your body start trying to fight the disease. These defensive white blood cells, also called B-lymphocytes, successfully form plasmocytes to produce antibodies and help your body fight off the disease. However, these antibodies take time to form, and by the time they develop, the person may have been infected and even cured.


The next time a person gets exposed to the same disease, the body has learned how to react and take quick action to fight off the disease. Vaccines work in much the same way. There are several types of vaccines, such as those containing genetic parts of the virus to guide our cells on fighting the disease, vaccines that insert innocuous pieces of the virus so that once our bodies are vaccinated, they can fight off the disease, and many more. Whatever the kind of vaccine, the ultimate aim is to equip our bodies and strengthen our immunity to help fight off the disease in the future.


Increased vaccination doesn't just protect the individual but helps to protect entire communities. As more and more individuals get vaccinated, there is a lesser chance of the virus infecting someone who is not vaccinated. This happens because a majority of the population is vaccinated. They have a lesser chance of getting the infection, so the infection rate is reduced even for a non-vaccinated individual. This process is called herd immunity and may take years to develop.


Especially in a highly contagious virus-like COVID-19, herd immunity can only develop when around 50%-90% of the population gets vaccinated.





How Long Does It Take Your Body to Develop Immunity After Getting Vaccinated?


Although most vaccines require two doses, some vaccines require only a single shot for a person to get fully vaccinated. Two shots are administered because the first shot helps start the phase in which your body creates protection, and the second shot helps to reaffirm and reimpose this process. Therefore, it can be said that one shot of the vaccine does not create a robust immune response, and so a second shot is needed to ensure it does. The patient cannot be administered both shots simultaneously and must wait a stipulated time frame to receive the second shot.


Even then, your body does not develop immunity instantly. It takes a while—around seven to fourteen days—to build immunity and be fully vaccinated. If you are infected after the second shot but fourteen days have not passed, you will not be considered vaccinated and may need to start the whole process again. While vaccines may boost your immunity for the first months, it is not sure how long vaccination will last in the long run, and a person may have to get vaccinated later again.





What Are Antibodies?


Antibodies are Y-shaped receptors that are produced to help your body fight off infections. When your body fights off infections such as COVID-19, the response helps develop antibodies produced with the help of your memory cells. Your memory cells contain and remember some parts of the virus remnants inside your body at the time of infection and thus develop antibodies as a response to help fight the same intruders in the future.


Vaccines work to develop antibodies by equipping your body with the tools to ward off infections. That is why people have reported experiencing side effects such as headaches, body pains, and slight fever upon getting vaccinated. Everyone won’t experience the same side effects because of differences in their genetic makeup.


What Will an Antibody Test Tell You?


Antibody testing is used to tell you whether your blood contains antibodies to help fight off the virus. A COVID-19 antibody test will assess whether you have already encountered COVID-19 or whether your body, once fully vaccinated, is ready to fight off the infection. However, it shouldn't be a surprise that your antibody test result can still come back negative even if you are fully vaccinated.


Positive Result: A positive test result will tell you that you may have had COVID-19 in the past and therefore developed antibodies as a result. This is not a surprise, even if you would have never thought you had the infection. Some people are asymptomatic in that they may get exposed and even get infected by the virus, but they do not experience the symptoms associated with the virus. As many as 40% of those people who get COVID-19 may be asymptomatic.


Negative Result: A negative test result indicates that your body has not encountered the virus recently. However, it is not confident that you may have had a COVID-19 infection sometime in the past. Since it usually takes around three months for antibodies to develop, it also means that they will reduce in the coming months.



The Different Types of COVID-19 Tests:


Although there is usually some confusion regarding the different COVID-19 tests, it is essential to remember that there are two kinds of tests for COVID-19 as approved by the FDA:


PCR test: A much more common kind of test and usually the one most used to determine the presence of COVID-19, it is tested through a nasal swab or throat swab. The fluid is then tested for a few days to determine if your body has COVID-19 germs and is usually the most accurate test out there. These tests are performed by health care professions, further confirming their efficacy.


Antigen test: Also called an antibody test, this test determines the presence of a spike protein of the coronavirus. This detection assesses whether you have had COVID-19 in the past and if your body has developed an immunity response.




The Different Types of Antibody Tests:


Antibodies may be present in your blood for several weeks after you've recovered from COVID-19 and may presume a level of immunity. Still, it is not sure how effective these antibodies maybe when it comes to protecting you against the virus. There are typically two types of antibody tests:


Binding Antibodies: These tests showcase one and one thing, and that is whether your body has developed or produced any antibodies as a result of recovery from COVID-19. They only detect antibodies but do not help point out how effective the immunization response is.


Neutralizing Antibodies: Once you've tested positive for antibodies, the neutralizing antibodies test comes in. A more novel test tests the efficacy of antibodies in terms of their immunization response. Therefore, it tests out whether your body can fight off the virus to analyze your immunization response towards COVID-19.


Do You Need an Antibody Test After Getting Vaccinated?


The real question is, now that you have gotten vaccinated, can your antibody test help you determine the efficacy of the vaccine? Indeed, this is not true because some individuals have gotten a negative antibody test result after getting vaccinated, indicating that their body has not developed antibodies and, therefore, immunity against the virus.


Since the vaccine is based on the coronavirus spike protein, it cannot be said for sure that an antibody test would indeed determine the presence of antibodies against this spike protein. An antibody is usually helpful in determining whether the patient has previously been diagnosed with the COVID-19 infection. It is not clear that an antibody may be because of a previous infection or because of the vaccine. A conclusion cannot be separated and drawn out.


Another essential feature is the accuracy of the antibody test. Even though the FDA has reviewed and approved the antibody test, certain things may go wrong or measures that have not been accounted for, such as sensitivity with regards to how precisely the test identifies between those who have been vaccinated or infected. The second measure is specificity, whether the test differentiates between those who were infected or vaccinated and does not include others at all.


There have been many cases with people reporting a false positive or false negative test, so the chances are that sometimes an antibody test can also be false, and conclusions should not be drawn from them. Therefore, neither can an antibody test determine the efficiency of the vaccine or assess the body's immunity from COVID-19.


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