How can you be positive

Positive corona test after Covid-19 vaccination - how can that be?

One thing is clear: the Covid-19 vaccination does not cause a positive corona test. This applies to both rapid tests and the more precise PCR tests. But why is that - after all, parts of the SARS-CoV-2 genome get into the body during the vaccination? In addition, after the virus information has been introduced, the body cells produce parts of the virus surface, the so-called spike proteins. These special proteins then set the desired immune reaction in motion, because the immune system evaluates them as foreign, reacts with defense measures and remembers them for later.

The PCR tests used only detect certain sections of the virus genome, but these are different areas than the areas that enter the body with the vaccination syringe. Such tests are therefore blind to the genetic material from the vaccination and do not respond to it. The quick and self-tests, called antigen tests, are very similar. They react to a specific virus protein. However, they don't care about the spike protein the cells produce after vaccination. The actual target of the antigen tests is the so-called N-protein, which envelops the genetic material inside the virus. If you find that, report "positive".

If it happens that a test shows a positive result shortly after the vaccination, it cannot be due to the vaccination. But it's not necessarily a mistake either. You have to take the result just as seriously as usual, because the following triggers are possible:

Contagion before vaccination

You can become infected at any time - even on the way to the vaccination appointment. If you were infected shortly before, you will not yet notice the infection. The viruses have to multiply in the body for a few days before the test detects them or the first symptoms appear.

Contagion after vaccination

You can also get infected after a vaccination, because the full vaccination protection does not unfold immediately after the spade. After the first vaccination, it takes about 10 to 14 days for partial protection to build up. The full effect is then only 7 to 15 days after the second vaccination. Only with the Johnson & Johnson vaccine is a single dose sufficient. In addition, the vaccines have different degrees of effectiveness, and none can prevent 100 percent of all infections. You can read more about the effectiveness of the Covid-19 vaccines here.

Wrong test result

All tests, even if performed correctly, have a certain probability of showing a false result. Both false positive and false negative. So it can happen that the test is positive even though you are not infected.

In addition, the different tests also have different degrees of sensitivity to the viruses. Some recognize lower amounts of virus than others. It can happen that one test is incorrectly negative while another is already correctly positive.

How can I be sure?

The likelihood of becoming infected after vaccination is low. Wrong test results are rare. Nevertheless, a positive rapid test result is treated in the same way as usual. You have to verify it with a PCR test. It is best to speak to your doctor by phone or go to a test center nearby. Until confirmed by the second test, you will need to isolate yourself.

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