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Blood sample for an antibody test
Photo: Marijan Murat / dpa
More vaccinations and quick booster vaccinations are central to breaking the fourth corona wave.
Experts from various disciplines have just presented this in a strategy paper for the coming winter.
The Standing Vaccination Commission (Stiko) currently recommends the third vaccination only for people over the age of 70 and some other groups, such as people with an immunodeficiency, but recently announced that it would make sense to offer the booster "in the medium term" to everyone.
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Therefore, if you are wondering how high your own immune protection is, you might also think about having the antibody level determined with the help of a test.
However, experts only consider this to be useful to a limited extent.
For COVID-19 vaccinations, Stiko does not recommend a general check of vaccination success with the antibody measurement, neither after the first nor after the second vaccine dose.
The only exceptions are people with an immune deficiency or an expected severely reduced immune response, for whom the success of the vaccination can be checked by a blood test.
"It is not expedient to do a completely non-directional antibody determination," says Andreas Bobrowski, chairman of the professional association of German laboratory doctors.
Above all, a test can provide important information to people who are generally susceptible to infections or who are immunocompromised as a result of treatments or illnesses.
Even people who “felt” nothing after their vaccination, that is, had no side effects, might be advised by their family doctor to have a test, says Bobrowski.
An antibody test usually checks the so-called anti-spike antibodies that are formed during the vaccination, explains Bobrowski.
For example, if you want to know whether you have gone through an infection, you should say so beforehand, because then you also have to check for so-called nucleocapsid antibodies.
No limit values set yet
It is not enough if the result is only a statement as to whether anti-spike antibodies are present in the blood.
The concrete values for which a standard of the World Health Organization (WHO) is used are important.
The value is given in BAU / ml, BAU stands for Binding Antibody Units.
But there are still no defined limit values from which someone is still considered protected.
Looking at data from his laboratory and from Israel, among others, Bobrowski says: Below a value of 21.8 BAU / ml, there is no measurable protection from anti-spike antibodies. Above this, however, there is a large gray area, where you don't really know when the protection against infection is sufficiently good. "In my estimation, a value of 500 is so high that you don't need a third vaccination immediately," says the laboratory doctor. With anything above 1000 BAU / ml one could speak of good protection.
The immunologist Carsten Watzl also commented on boosters and the antibody tests on Twitter. With a view to the study situation, he writes that the protection is probably very low at below 50 BAU / ml, but probably good at over 1000 BAU / ml. "But in between, nobody can make a serious statement about protection." He emphasizes that when there is a question about limit values, it is about protection against symptomatic infection. The protection against a serious illness can still be high even with low antibody levels.
In addition, in addition to the anti-spike antibodies, the activated T cells, called memory cells, are also important for immune protection.
"These are the guards who stay longer and provide cellular protection when the virus comes back," explains Bobrowski.
Their presence can be determined using T-cell tests.
This means that just because an antibody test shows low BAU / ml values does not necessarily mean that there is no longer any immune protection against the virus.
Because the immune system also consists of a cellular defense.
Booster is not dangerous even if the antibody level is high
If their antibody level is high, many people would assume that they should not receive a booster vaccination, writes the RKI on its website.
But that is wrong.
Even with the immunity still in place, there are no security concerns with regard to the refreshment.
There are uncertainties with the antibody tests.
Errors can occur when removing from the fingertip that falsify the result.
For example, when the skin is pressed to squeeze out a little blood, as laboratory doctor Bobrowski says.
"Tissue fluid can also get into the blood." From his point of view, a collection from an elbow vein is always the better option.
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Some providers offer antibody tests in which the blood sample is evaluated on site in a small analyzer. So you get your value promptly sent on the day the blood was taken. He cannot provide any information on the quality of these machines, says Bobrowski. There is not yet enough validation data available for this. However, he sees greater uncertainties in the quality of the results of these small devices than in the case of the automatic analyzers in an accredited and medically managed laboratory. When in doubt, Bobrowski advises asking how the quality of the analysis is ensured - providers should then be able to provide more answers than just referring to the device manufacturer. But of course, even then, laypeople find it difficult to estimate how reliable the results really are in the end.
The antibody tests are usually not covered by the health insurance, so you have to pay for them yourself.
According to the official fee schedule, a laboratory can charge EUR 17.49 for an antibody test, says Bobrowski.
Doctors would also receive around four euros for taking blood samples.
This official price is appropriate for an antibody test in which the effect of vaccinations that have already been carried out is checked.
If providers demand more than 40 or 50 euros for the determination of the IgG antibodies, this is by no means justified.
mar / dpa