The elderly and people with compromised immunity are advised to get the fourth coronavirus vaccination. But do most German citizens also benefit from this? So say the experts.
Is a fourth vaccination against Covid needed? The answers to this question could not be more varied: while Federal Minister of Health Karl Lauterbach (SPD) recently defended a second booster from the age of 18, the Standing Vaccination Commission (STIKO) currently recommends only a second booster for over 70 years- the elderly and people with previous illnesses. If the proposal of the European Medicines Agency (Emma) were to go, it would be the turn of only the elderly over 80 years old. On the other hand, the US has set the age limit of 50 years. Especially for young people, the question arises about the benefit of a fourth dose of vaccination – especially since a completely new vaccine against the omicron variant is in perspective from the fall. What the experts say:
What happens after a vaccination?
In the so-called immune response, on the one hand, antibodies are formed: these include neutralizing antibodies which – if present in sufficient quantities – can prevent infection with the Sars-CoV-2 virus. However, this protection is only temporary and ends after a few weeks, because the amount drops, says Christoph Neumann-Haefelin, head of the Translational Virus Immunology working group at Freiburg University Hospital. Another important part of the immune response is the formation of so-called T cells. “These can shorten an infection and provide a smooth course,” says Neumann-Haefelin. And this protection lasts a long time. “Therefore, one must be aware that protection against infection through boosters cannot be guaranteed.” Rather, it is about protection from severe courses.
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Is another booster vaccine needed to increase protection?
Anyone vaccinated now for the fourth time will not reduce the risk of Covid 19 infection to zero. Although the number of neutralizing antibodies has increased again for a while, the amount is not enough to provide complete protection against the omicron variant. Neumann-Haefelin points out that an amplifier does not necessarily have an advantage for the T cell response in healthy people. “The T cell response in healthy people is relatively strong after only two vaccinations.” It has been shown that although the number of helper T cells in the blood increases after a third vaccination, it immediately drops back to baseline. “In young, healthy, boosters are not currently improving the T cell response.” However, it should be expected that the T cell response also decreases over time – and subsequent boosting shots may contribute to sustained defense.
Who should promote?
Stiko currently recommends a second booster only for people over 70 and people with previous illnesses. And rightly so, says Christine Falk, President of the German Association for Immunology and a member of the Federal Government’s Council of Experts on Corona. “There are people whose immune response to vaccination is not particularly good.” This applies to patients with congenital immune defects or those who have had an organ transplant or are undergoing cancer therapy. Because they often take drugs that suppress the immune system. However, to a lesser extent, this also applies to older people. “They respond much more slowly to vaccination,” says Falk. Only after the third or fourth vaccination do they have an immune function similar to that of healthy people after the second vaccination.
Who does not need a booster these days?
For healthy young people, a booster does not bring any advantage at this point in time: “The previous vaccination works very well,” says Falk, who heads the Institute for Transplant Immunology at Hanover Medical School. “Even if the antibodies and T cells are reduced, this should not be a concern: they do not disappear.” The immune system pushes them to a low level for economic reasons. And these can be reactivated quickly.
Can you grow up very, very often?
Experts such as Andreas Radbruch, Scientific Director of the German Center for Rheumatic Research in Berlin, warn that the immune system becomes saturated if vaccinations are given too often continuously: there is no longer an immune response. “The processes in the body to build an effective immune memory are complex and time consuming,” says Radbruch. The expert waits at least six months for this. Healthy people should definitely wait for this period of time before using boosters. On the other hand, the result is very stable: once the so-called affinity maturity is completed, a protective effect up to 100 times higher than directly after vaccination is achieved with ten times less antibodies. “And these very good antibodies are transferred to immunological memory,” says Radbruch. “The cells that make them migrate to the bone marrow and survive there for decades.” The protection thus remains permanent.
What should be the time interval between the third and fourth vaccination?
There is no optimal time interval, says Freiburg expert Neumann-Haefelin. “But it would be important for healthy young people to maintain a minimum interval of six months.” Vaccination protection probably lasts much longer. So it is enough to strengthen yourself by autumn. In the elderly or patients who are not expected to have a good immune response, the fourth dose should be given earlier – after about three months.
With which vaccine should you improve yourself from the fall?
That’s hard to say in advance, says Freiburg immunologist Neumann-Haefelin. It depends on which variant of the virus is in circulation at that time. “I do not think you can make a big mistake with any variant.” Although the customized Omicron vaccine would offer an advantage in terms of antibody protection, it would only last a few weeks. “Protection against a severe course, on the other hand, is not affected by the choice of vaccine.”
For whom does it make sense to measure the number of antibodies before vaccination?
Basically, the level of antibodies in the blood shows little about how well the vaccine works. Exceptions are people with weakened immunity, explains immunologist Falk. Studies with people who have had heart or lung transplants have shown that no antibodies could be detected in the blood of 60 percent of those affected after vaccination. This can also happen to other people with compromised immunity and the elderly who need care. “A measurement may be appropriate here to find out if a basic immunization has been achieved with the help of the first three vaccinations or if a booster is still needed.”
Can you reduce the viral load on the body with a fourth vaccination so that you are less contagious?
This question has not yet been clarified. According to immunologist Neumann-Haeflin, the data show that a new booster vaccine causes a small drop in viral load. “But the question is whether this really reduces the risk of infection for others.” But there are legitimate doubts about that.