A booster vaccination against corona is now recommended for all adults. But when is it best? Is your protection still adequate or do you need a refresher? Here’s how you can test it.
While the number of infections is still at a record high and the new Omikron variant is also a cause for concern about the coronavirus, experts are now advising every adult to have a booster vaccination. The aim is to strengthen the immune protection against SARS-CoV-2.
Usually the third vaccination is recommended six months after the second. However, depending on the immune system, age or previous illnesses, the protection may decrease beforehand. There are a few ways to find out if you should get a booster vaccination sooner.
How work T cells and antibodies?
Basically, immunity against a virus arises when the immune system comes into contact with the pathogen directly or only with individual parts of it. This contact triggers an immune reaction in the body and on the one hand antibodies and on the other hand immune cells are formed.
Antibodies are proteins that can neutralize pathogens such as bacteria or viruses. T cells on the other hand, white blood cells are those that recognize structures foreign to the body when they are presented on an endogenous cell. In the case of the corona vaccination, it is mainly those who play T memory cells play an important role, as they can react quickly and protect the body in the event of repeated contact with the same pathogen.
How can you measure your antibodies?
There are different types of antibody tests to determine how many antibodies you have made against the coronavirus.
On the one hand, there is the possibility of determining the antibodies in the blood, the so-called antibody titer. Meanwhile, there are also some of these tests that can specifically detect antibodies against the spike protein of SARS-CoV-2. “One can assume that these antibodies actually ensure an effective immune response in contact with the virus,” says Professor Gregor Rothe, head of the Institute for Laboratory Medicine at the Marienkrankenhaus in Hamburg, in the pharmacy shop.
Antibody test: Everyone can test how many antibodies they have against the coronavirus at home. (Source: Rolf Poss / imago images)
On the other hand, there are also so-called neutralization tests, which are actually only used for research because they bring blood serum into connection with coronaviruses. Then a check is made to see whether the viruses can be stopped. In simplified procedures, the blood serum is only associated with harmless parts of the coronavirus. However, the informative value of these tests is limited. “It cannot be said for sure how pronounced the immune response actually is,” says Dr. Matthias Orth, chief physician of the Institute for Laboratory Medicine in the Marienhospital Stuttgart on the pharmacy review.
Carsten Watzl, immunologist from Dortmund, explains this: The neutralization tests are more precise than the determination of the antibody titer, but the amount of antibodies is also important.
And finally, there are tests that only indicate whether there are antibodies against the coronavirus or not. These tests can only be used to check whether someone has ever had contact with SARS-CoV-2 and, for example, was ill without symptoms. These tests are only suitable for unvaccinated people and they are only of limited informative value.
How will T cells checked?
Since antibody tests do not provide any information about immune memory, they also play T cells an important role. The answer of the T cells is difficult to measure, however. There are now tests for this, too, but they are rarely used in practice and, above all, in research.
In one test variant, the blood to be examined is divided into two pools. One pool is stimulated with the virus antigen, the second is not. “So we could T cells identify that respond to the virus and characterize an exact phenotype, “said Dr. Herbert Schiller, research group leader at Helmholtz Zentrum München in August when he presented his study.” So we now have a profile of one T-cell, who fights SARS-CoV-2. “
At which limit values is a booster vaccination necessary?
There are no satisfactory answers to this question either. In principle, there are no fixed values according to which someone is considered protected or unprotected.
A study from the USA recently showed that from a value of 1,000 BAU (Binding Antibody Units, a unit for antibodies in the blood), there should be a very high level of protection against Covid-19. On the other hand, the expert Andreas Bobrowski, chairman of the Professional Association of German Laboratory Doctors, told “Spiegel”: If the value is below 21.8 BAU, there is no longer any measurable protection from antibodies. Above this there is a large gray area, within which one does not know exactly how good the protection is. “In my estimation, a value of 500 is so high that you don’t need a third vaccination right away,” he explained.
The immunologist Carsten Watzl expressed a similar opinion: The protection below 50 BAU is probably very low, but with more than 1,000 BAU it is good.
However, other studies show: A low antibody concentration does not automatically mean that there is no longer any immune protection. And a high concentration does not automatically protect against infection.
Is a test of antibodies and T cells before the booster vaccination makes sense?
You can come up with an antibody or T cell test give you a rough idea of how your immune protection is doing. However, the tests should not serve as a clear recommendation for or against a booster vaccination.
The Robert Koch Institute, for example, also explains: “According to the current state of knowledge, serological detection of SARS-CoV-2-specific antibodies does not allow a clear statement about infectivity or the immune status.” Reasons for this include the low informative value of the tests, but also the “considerable differences” in the results of the tests. The RKI therefore also emphasizes: “A high antibody titer does not speak against the implementation of a vaccination.”
Stiko also contradicts the idea of using the antibody level to check the vaccination status: “Stiko does not recommend a general check of vaccination success for Covid-19 vaccinations, neither after the first vaccine dose nor after the second vaccine dose.” However, there is an exception for the serological control in certain patients with an expected greatly reduced vaccination response.
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