Researchers have examined a man in Germany who claims to have received 217 vaccinations against COVID-19 and found that his immune system was fully functional.

Until now, it has been unclear what effects hypervaccination such as this would have on the immune system. Some scientists were of the opinion that immune cells would become less effective after becoming used to the antigens.

However, the case study published in The Lancet Infectious Diseases journal found that the immune system of the person is fully functional.

More than 60 million people in Germany have been vaccinated against SARS-CoV-2, a majority of them several times, the researchers said.

The man examined by a team at Friedrich–Alexander University Erlangen–Nurnberg (FAU) in Germany claims to have received 217 vaccinations for private reasons. There is official confirmation for 134 of these vaccinations, they said.

"We learned about his case via newspaper articles," said Kilian Schober from FAU.

"We then contacted him and invited him to undergo various tests in Erlangen (a city in Germany). He was very interested in doing so," he said.

Vaccinations contain parts of the pathogen or a type of construction plan that the vaccinated person's cells can use to produce these pathogenic components themselves.

Thanks to these antigens, the immune system learns to recognise the real pathogen in the event of a later infection. It can then react more rapidly and forcibly.

The researchers wanted to analyse what happens if the body's immune system is exposed extremely often to a specific antigen.

"That may be the case in a chronic infection such as HIV or hepatitis B, that has regular flare-ups," explained Schober.

"There is an indication that certain types of immune cells, known as T-cells, then become fatigued, leading to them releasing fewer pro-inflammatory messenger substances," he added.

This and other effects triggered by the cells becoming used to the antigens can weaken the immune system, which is then no longer able to combat the pathogen so effectively.

However, the study does not deliver any indication that this is the case, the researchers said.

"We were also able to take blood samples ourselves when the man received a further vaccination during the study at his own insistence. We were able to use these samples to determine exactly how the immune system reacts to the vaccination," Schober said.

The results showed that the individual has large numbers of T-effector cells against SARS-CoV-2. These act as the body's own soldiers that fight against the virus, the researchers said.

The person even had more of these compared to the control group of people who had received three vaccinations, they said.

The researchers did not perceive any fatigue in these effector cells. They were similarly effective as those in the control group who had received the normal number of vaccinations.

They also explored memory T cells -- cells at a preliminary stage, similar to stem cells, that can replenish numbers of suitable effector cells.

"The number of memory cells was just as high in our test case as in the control group," explained Katharina Kocher, one of the leading authors of the study.

"Overall, we did not find any indication for a weaker immune response, rather the contrary," Kocher added.

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