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Booster against Corona: For whom are further vaccinations useful?

A man from Magdeburg had himself vaccinated against Corona a whopping 87 times last summer – probably mainly to get vaccination certificates in this way, which he then sold on to vaccination skeptics who wanted to circumvent the corona restrictions without being vaccinated . Investigators uncovered this curious case in early April. Is the 62-year-old particularly well protected from the virus thanks to the many vaccinations? And would a second booster, i.e. a fourth vaccination, also be worthwhile for the rest of the population? After all, excess vaccine is currently being disposed of because it has expired.

In a press conference with the Science Media Center, immunologists decidedly dismissed this. They emphasize: In immunologically healthy people, an additional vaccination tends to disrupt the process of maturation of the immune response and thus probably does more harm than good.

More boosters: More vaccinations could disrupt the maturation of the immune response

For the general population, another booster vaccination would not make sense until autumn at the earliest, when a vaccine adapted to Omikron would be available. If any. Because a process called affinity maturation takes place in all vaccinated people, explains Professor Andreas Radbruch, director of the German Rheumatism Research Center in Berlin. “The concentration of antibodies against a certain virus in our body decreases. But those that remain or are newly formed bind better and better to the receptors of the virus.”

To a certain extent, such mature antibodies could even recognize new virus variants that are still to come. There is a race between the virus and the immune system, but our defenses are sometimes even prepared for future virus developments. However, further vaccinations disrupt this process of maturation. “Because the fact that the virus antigens are becoming increasingly scarce in the body is crucial for maturation”. With each new contact – for example through further vaccinations – many antibodies that do not match well would be formed again.

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Mucosal immunity crucial – but poorly understood

In addition, those who have been vaccinated usually still have good protection against serious illness. This is due to the T cells, part of the so-called cellular immune response that is formed during a vaccination. These T cells, which cannot prevent an infection but can greatly reduce it, are hardly affected by the mutations in omicron. More and more studies show this.

Andreas Radbruch also argues that the decreasing amount of antibodies in the blood is not the reason why tens of thousands of vaccine breakthroughs have occurred. Rather, it plays a role in how many antibodies get from there to the mucous membranes of the respiratory tract. This usually only happens a relatively short time after vaccination. “Unfortunately, this process is still very poorly understood,” says Radbruch. It is therefore unclear how the so-called mucosal immunity can later be increased again.

Immunocompromised people should take boosters more often

An exception are people whose immune system is severely weakened. For example, anyone who is being treated with chemotherapy for cancer, who has to take immunosuppressive drugs after an organ transplant, or who is very old and therefore weakened, could well make sense for further booster vaccinations, as recommended by the permanent vaccination committee, emphasizes Christine Falk . The immunologist from Hannover Medical School is also a member of the German government’s Corona Expert Council. “In such people, it can also be useful to have antibodies detected during a vaccination, simply so that you can see whether there is an immune reaction at all.”

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Professor Christoph Neumann-Haefelin from the University of Freiburg also thinks it makes sense to vaccinate immunocompromised people repeatedly. “Their immune system often only kicks in after the third, sometimes even after the fourth vaccination,” he says, referring to various clinical studies. For all other people, however, the following applies: A longer interval before a new booster vaccination makes a lot of sense. At least six months should have passed.

True immune escape variant could theoretically arise

In view of the development to date, it is unlikely that the corona virus could change as quickly as the flu pathogen influenza. The heavily mutated omicron variant is also largely identical to the original virus. An annual vaccination with an adapted vaccine will in all likelihood not be necessary.

“It’s not very likely, but theoretically it could happen that a variant develops that can actually evade immunity from the T cells,” concedes Neumann-Haefelin. In this case, however, vaccination with the existing vaccines is of no use, then they would have to be adapted. “Fortunately, mRNA technology gives us a method that we can use to create adapted vaccines very quickly,” he says.

Immunity against Sars-CoV-1 still available after 19 years

According to Andreas Radbruch, experience with the corona precursor Sars-CoV-1 shows that this scenario is very unlikely. Tests there showed that people who had the virus 19 years ago still have antibodies in their blood that can switch off the pathogen.

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