D.he recommendation by BioNtech / Pfizer for a third “booster” vaccination increases the pressure on politicians and authorities to include antibody tests to prove the immune status of vaccinated and convalescent people in the national test strategy. At the beginning of the week, the umbrella association of German diagnostics companies called for a “realignment” of the federal test strategy in a separate position paper in order to gain more clarity about the immunity situation in the population. According to the will of European parliamentarians, antibody tests should also serve as proof of immunity for the digital Covid-19 certificate.
The initiative, however, failed because of Brussels and objections from national governments – including German governments. For the Robert Koch Institute, the indirect proof of a past infection with the antibody tests or the proof of an existing immunity after vaccination or infection are not conclusive enough. “According to the current state of knowledge, a serological detection of SARS-CoV-2-specific antibodies does not allow a clear statement about infectivity or the immune status,” it says there.
In fact, there is a growing need to know one’s own immune status. “Hundreds of thousands of antibody tests are now carried out in the country every week,” says Thorsten Hilbich, Vice President of the Association of the Diagnostics Industry (VDGH). The tests also have to be paid for by statutory health insurance patients themselves. The study presented this week at the University of Mainz is also likely to have increased demand, according to which the 3.7 million Covid-19 recovered people recorded by virus evidence were added to many unnoticed infections caused by those infected without symptoms. Almost forty percent of the infections turned out to be asymptomatic in the Mainz antibody study, which means that in addition to those who have recovered, who hardly know anything about their current immune status, there are hundreds of thousands or millions of citizens who would like to know how many doses of their vaccine they have Need protection.
The diagnostic laboratories see the offer to learn more about one’s own immune status with antibodies, according to Hilbich, as “an additional motivation” that could give the national vaccination campaign an additional boost. In the VDGH position paper, the companies speak of the “momentum” that should be used to strengthen confidence in the vaccinations. In addition, the inclusion of an antibody test and thus a proven immunity in the digital vaccination certificate could further reduce the shortage of vaccines and could be accompanied by “step-by-step easing steps”.
Doubts of the professionals
How useful the antibody tests are for this is currently not only being questioned by the Robert Koch Institute. In many countries, including the USA, scientists and immunologists warn against overestimating the informative value of antibody tests. The range of rapid tests and laboratory-based professional tests is enormous, for some a drop of blood from the fingertip is enough, and the antibody test market is practically already established at costs of ten to more than thirty euros per test.
However, diagnostic expert Hilbich also points out that although many of the tests meet the minimum requirements of the World Health Organization and can detect certain antibodies in the blood, they do not provide precise information about immune protection. In general, it is still far from clear which threshold values have to be exceeded for which antibodies and immune cells so that the persons concerned are really protected from infection.
Basically, only those antibodies from the blood serum that are directed against the binding molecule of the Sars-CoV-2 virus and for which virus neutralization tests have shown that they actually represent the pathogen in circulation – and thus also the variants – are considered meaningful. attack. In the end, this gives a test value, which, however, is by no means considered sufficient by all experts because of the very different immune responses in people.
In addition, experts believe that solid immunological statements about a weakening immune system are not possible as long as the second line of defense (T cells) or the temporal course of the antibody levels are not taken into account. Such considerations have so far played no role in the National Test Strategy. For Hilbich this is a fatal deficit: “If the number of cases increases, we urgently need to think about strategies to systematically test the vulnerable groups, especially in old people’s homes.”