After recovery from Corona virus infection or after vaccination, antibodies against the Spike protein are created in humans. SARS-CoV-2 uses this protein to attach to cells and penetrate them. From the Spike protein, antibodies can detect the virus, attach to it, and make it “understandable” to the cells of the immune system.
Prof. Carsten Watzl, Leibniz Institute, Dortmund Technical University
For mRNA vaccines such as BioNTech / Pfizer, researchers believe that those vaccinated are over 90% protected against the virus, but after the Delta variant, which is more contagious, this protection is lower and the virus manages to infect humans. who have only received the first vaccine. Immunologist Carsten Watzl of the Leibniz Institute at the Technical University of Dortmund estimates that the effectiveness of the BioNTech vaccine drops to 88%, while that of vector vaccines such as AstraZeneca drops from 66% to 60%. Data from Israel even speak of a 64% protection with the BioNTech / Pfizer vaccine. The Ministry of Health is considering a third vaccination.
Delta variants is putting researchers in front of great challenges. So far most of us at best after two vaccinationsare immune to known variants of the virus. But that does not include everyone who gets vaccinated, says immunologist Carsten Watzl. “The vaccine alone does not guarantee that you are immune. Crucial is that our body has created the right defenses. But we can not measure this accurately enough so far. “
The case with the tetanus vaccine is different. If we do not know, if we have enough protection, then we can measure this with laboratory tests. If the number of antibodies is above a certain value, then the person is immune to the virus, if the value is low, the doctor may recommend repeating the vaccine.
“Regarding Corona, we have not reached this stage yet. We do not know exactly what to measure in order to really determine if someone has been immunized or not. Neutralizing antibodies most likely play a crucial role because they “bind” the virus so that it does not infect other cells. “But how high the number of antibodies should be is still unclear,” said expert Watzl.
The role of T lymphocytes
Not only antibodies are important in fighting an infection. If the virus has penetrated the body, the antibodies can no longer reach it because they cannot reach the cells. The virus is added. “To fight the virus, our immune system has T lymphocytes. They are able to identify and eliminate infected cells. “So we sacrifice some infected cells in our body to keep the virus from multiplying,” explains Carsten Watzl. These can be measured both, but it is practically difficult to identify the number of T cells. This test is difficult but valuable. “Antibodies alone do not necessarily tell you how protected you are. “It may happen that I have very few antibodies and become infected with the virus, but the T cell response is so strong that I do not get seriously ill.”
There are various tests that measure antibodies against Corona. Laboratories normally have a clear standard, ranging from a minimum to a maximum. The doctor can tell if the values are within the allowable range, but in Corona this is not precisely defined. It can only be said approximately. Measured values range from less than one hundred to several thousand antibodies. “If I’m in the top quarter or the top half, I probably have a good immune defense. But I can not say the exact value of this. “
It is also not clear how fast a level of antibodies falls, it is only known that with time it falls. “This is done in two phases. If you look at the values immediately after vaccination, you have the highest level of antibodies. In the first months after vaccination, this value drops rapidly. “But at a certain moment everything stabilizes around a certain value and it continues to fall more slowly, we know this from other vaccines and it seems that it is the same with the Corona vaccine”, says the expert, but it has not been proven yet personally scientifically.
The more the better
There are people who have been vaccinated twice, and do not have or have very few antibodies against the Corona virus. These people are not protected from the virus, most likely, warns Watzl. There are many factors that lead to a low level of antibodies. Age is one of them, but also a weakened immune system that does not function as in healthy people and can not be properly protected from “attacks” from outside. A third vaccine often needs to be given for the body to start making antibodies. Expert Conclusion, Carsten Watzl so far: More helps more./DW