Corona current
Is it true that rapid tests do not work in people who have been vaccinated?
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The corona infections continue to rise, while there are rumors that rapid tests in vaccinated people would not work at all. We asked a doctor.
Germany is currently breaking new records every day for the highest number of new infections since the beginning of the corona pandemic. Meanwhile, calls for free tests are getting louder again – even for those who have been vaccinated. But can a rapid test like the one you can currently buy in the supermarket even detect the coronavirus if you are vaccinated?
How can it happen that rapid tests in infected vaccinated people turn out negative?
Vaccination breakthroughs are reported again and again, in which the rapid test is said to be negative at first, but the PCR test is positive. Since this news is increasingly causing uncertainty, we asked a doctor. Professor Thomas Löscher is a doctor for internal medicine, tropical medicine and infectious diseases in Munich and explains negative rapid tests despite the corona vaccination as follows: “In the case of breakthroughs in vaccination, the virus excretion is usually much lower and shorter, so that this is more often not recorded by the rapid antigen tests, while the highly sensitive PCR method also detects small amounts of virus.”
The viral load seems to be so low in vaccinated people that it is sometimes not recorded by rapid tests – especially at the beginning of an illness. In addition, there is incorrect handling, because testing at home still contains sources of error: “However, the type of sampling also plays a role – A proper deep nasal / throat swab carried out by health personnel is much more sensitive (but also much more uncomfortable) than a nasal swab, spit test or lollipop test carried out by laypeople, “warns Prof. Löscher.
Not all corona tests are equally effective
In addition to the viral load and sampling, there is a third factor that influences whether or not a rapid test works in infected vaccinated people: “After all, there are also clear differences between the various makes of rapid test“, says Prof. Löscher. Experts from the Paul Ehrlich Institute have currently examined 122 Covid antigen rapid tests for their sensitivity – that is, their ability to detect the coronavirus. 26 of the tests failed.
Test manufacturers can state the sensitivity of their tests themselves until May 2022, so the products are certified by the manufacturers themselves. From next year this security gap should be closed and the tests carried out by EU-approved laboratories, writes the Paul Ehrlich Institute.
The Federal Institute for Drugs and Medical Devices has one so that consumers can find their way around the current jungle of many rapid tests in shops List of examination results released. Here you can see exactly which of the tests have a high sensitivity of 100 percent and which less. At the same time, the detectability of the coronavirus with high and low infectiousness can be read.
“With the appropriate quality, rapid antigen tests allow acutely infected and potentially infectious persons to be identified promptly and enable immediate measures to curb the spread of the virus,” writes the Paul Ehrlich Institute. The tests can therefore continue to be a security level to protect yourself and others – even with vaccinated people. However, one should make sure that these are carried out thoroughly and with appropriately effective tests.
To protect against breakthroughs in vaccination, Prof. Löscher finally recommends the currently discussed booster vaccinations: “Especially for immunocompromised people, the elderly and the chronically ill. With these, an antibody test one to two months after the basic vaccination (two vaccinations) is useful. Ultimately, however, we need a booster vaccination for everyone. “
sources used: Interview with Prof. Thomas Löscher, Paul Ehrlich Institute, Federal Office for Drugs and Medical Devices