In the pandemic, antibody tests are an important indicator of the impending danger of Sars-CoV-2. Experts explain what’s really behind it.
Frankfurt – “The third wave seems broken,” summed up Federal Health Minister Jens Spahn * recently. The 40-year-old CDU * politician thus nourished the hope of normalcy. After more than a year of the corona pandemic, Germany is picking up the speed of vaccination.
At the same time as these developments, insecurity among the population is growing. For example, many people want to know whether they are protected against the coronavirus after a vaccination or surviving Covid 19 disease or how meaningful antibody tests actually are. Experts provide answers to these important questions of the crisis.
Corona pandemic: antibody tests can play a key role
There is currently no one hundred percent method of providing vaccinated or recovered people with reliable information about their risk of re-infection. However, what definitely does its part to clarify the situation are so-called antibody tests. There are essentially two variants of this. On the one hand, there are tests that can measure whether the respective person was already infected with Sars-CoV-2 – or not. On the other hand, there are tests that can check how well the antibodies that are formed are working.
In so-called neutralization tests, the patient’s blood serum is brought into contact with coronaviruses under laboratory conditions. A reaction then shows how functional the antibodies are. “The better the antibodies dock, the less serum I need for it,” explains Thomas Lorentz, laboratory doctor and board member of the Association of German Laboratory Doctors. In the next breath, however, he emphasizes that neutralization tests can never give absolute certainty. However, he states: “A positive neutralization test almost always means that you are protected.”
Corona pandemic: after infection, the number of antibodies decreases
Carsten Watzl, immunologist at the Leibniz Institute of TU Dortmund University, adds Lorentz’s remarks: You have to differentiate between the amount of antibodies and the amount of neutralized antibodies. “In other words: if I have a lot of antibodies in my blood, it is highly unlikely that all of these antibodies will not be in the right place on the virus,” says Watzl. The pure amount can be determined by an antibody test.
A statement about the amount of antibodies from which the immune system is protected from the coronavirus seems almost impossible to the experts. “Nobody can tell you at what level you are really immune,” says immunologist Watzl. However, research is aware of the fact that after a corona infection the number of antibodies decreases after a certain time: “The big question is whether and until when immunity still exists. We don’t know, ”stresses laboratory doctor Lorentz. There are only a few known cases against the possibility of re-infections.
Coronavirus: These antibodies exist
In the fight of the immune system against coronaviruses, three variants of antibodies are particularly relevant:
- IgA and IgM antibodies: If coronaviruses are identified in the blood, they are formed relatively quickly. However, after infection with the virus, their blood levels drop faster than other antibodies.
- IgG antibodies: These antibodies are formed in the long term. So-called memory cells, which store a lot of information about the virus, are responsible for this. “Anyone who still has these memory cells can quickly produce many new antibodies if necessary,” says immunologist Watzl. IgG antibodies stay in the blood much longer.
Corona antibody tests: how they work – what they cost
According to laboratory doctor Lorentz, a simple antibody test that shows whether a person has already been infected with the coronavirus or not costs 17.50 euros. Neutralization tests, on the other hand, cost up to 60 euros, according to Lorentz. This applies to antibody tests in which a doctor takes blood from the person and then analyzes it in the laboratory.
There are also self-tests at home, which the laboratory doctor advises against. According to Lorentz, patients often find it very difficult to take a blood sample and afterwards do not know how to classify the result. Such a test is priced between 50 and 70 euros. “You can have that done sensibly by your family doctor,” says the laboratory doctor.
Corona: Antibodies protect against mutants
Experts attribute a large part of the new infections with Sars-CoV-2 in Germany to different Corona variants, such as the mutant B.1.1.7. According to the Robert Koch Institute, the proportion of the Indian variant has increased comparatively strongly in recent weeks. The World Health Organization (WHO) called the global development in this regard “worrying”.
Common vaccines, such as those from Biontech / Pfizer or Moderna, protect against various mutants of the virus. “Changes can occur in the spike protein of the virus, so that the antibodies developed after the vaccination no longer fit so well – which means that the immune response to certain variants is no longer so good,” explains Marcus Panning, virologist at the Freiburg University Hospital. Nevertheless, since the protection against virus variants “still okay”. What is prevented with great certainty is a severe disease course of Covid-19.
“Vaccinations protect relatively reliably against a fatal outcome. This is also assumed for those who have recovered. “
Regardless of whether a person has been vaccinated or recovered, antibody tests do not serve as evidence in the debate about corona relaxation. * “Vaccinations protect relatively reliably against a fatal outcome. This is also assumed for those who have recovered “, says immunologist Watzl – and explains:” There are people who have hardly any antibodies after a few weeks, others still have many after 300 days – that is too complicated to handle the openings. “
Antibody tests therefore serve more as a source of information for one’s own environment or about one’s own immune system. A regular test is particularly useful for people with previous illnesses. For this purpose, experts recommend a neutralization test to examine how functional the antibodies actually are in the organism. (tu / dpa) * fr.de is an offer from IPPEN.MEDIA.
