Coronavirus: Why you are immune after a vaccination

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If you become infected with the Sars-Cov-2 coronavirus, the body activates its immune response. It begins to form antibodies, antibodies floating in the blood. So-called neutralizing antibodies are important, explains Rudolf Valenta, Head of the Department of Immunopathology at MedUni Vienna. These prevent the virus from entering human cells.

Vaccination provokes an immune response

Whether every person develops such protective antibodies or not is a matter of dispute in science. “In a study we found that only 40 to 50 percent of people make strongly neutralizing antibodies,” reports immunologist Valenta. Interim results of his investigations were published in the journal “Allergy” in the summer. In the meantime he has been able to expand his examination to several hundred patients. The researchers of antibody studies carried out in Innsbruck and across Austria point out, however, that they were able to detect neutralizing antibodies in almost everyone who had recovered.

The vaccination against the coronavirus provokes the same immune response in the body as with an illness by giving the body the instructions for the corona-specific spike protein. “Then an immune response arises and it is roughly comparable to the one that arises when someone has had an infection,” says Valenta. If a person does not develop neutralizing antibodies, this is not a problem, since vaccination protection is not based solely on antibodies, but also on T-cell immunity. “In one case, the patient is completely protected when he has a lot of antibodies, because then the virus cannot even multiply in the body,” says the immunologist. “In the other case, the body is prepared, already has an immunological memory and can then respond quickly.”

T-cell response also protects

The body not only reacts to the virus with antibodies, but also trains its immune cells in the event of a vaccination or infection. They are programmed to Sars-CoV-2 and an immunological memory is formed, explains Alexander Scheffold, Director of the Institute for Immunology at the University Medical Center Schleswig-Holstein. “After the answer is over, the cells retire, but they remember what they have learned. That is why they are called memory cells. ”The next time the pathogen enters the body, the immune response will be much better and stronger thanks to these memory cells. In most cases there is no longer any disease.

Just like a disease, vaccination leads to such a T-cell response and the formation of memory cells. That would be shown by the available data from the vaccine manufacturers, emphasizes Scheffold. How long this primary vaccination protects the body, this question is still open. Rudolf Valenta also agrees. Statements about this can only be made when further waves of infection have survived.

Coronavirus infections that have gone through do not protect

The Cluster of Excellence Precision Medicine in Chronic Inflammation (PMI) from Kiel has now been able to refute the hope that one would also be immune to the novel coronavirus SARS-CoV-2 due to colds that have already been triggered by other coronaviruses. In their study published in the journal “Immunity” they show that existing memory cells supposedly recognize parts of the SARS-CoV-2 and start an immune defense, but this immune response is inadequate.

“Someone who gets older has much more interaction with a wide variety of foreign substances in the course of their life, that is with a wide variety of viruses, bacteria, fungi and so on,” explains Petra Bacher from the Institute for Immunology at the University of Kiel. The immunological memory of older people is greater and thus the probability that the body will react with existing memory cells in the event of a SARS-CoV-2 infection. Instead of sending off so-called naive T cells that learn within one to two weeks to act against the specific pathogen, the likelihood that existing memory cells will be used increases with age.

“We have seen that these pre-existing memory cells in people who have not yet had contact with SARS-CoV-2 do not generate an optimal response against the virus,” says the professor of immunology and immunogenetics. “And we also saw this not particularly good answer in patients who have a severe course of Covid-19.” The immunological memory that is more pronounced with age could therefore explain why older people are at higher risk have a severe course of disease with Covid-19.

Juliane Nagiller, Ö1 Science





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