How the booster vaccine increases protection against omicron


The omicron variant of Sars-CoV-2 also infects many vaccinated and recovered people. Nonetheless, after three doses of an mRNA vaccine, one is highly protected from serious consequences. But how can it be explained that booster shots based on the original strain of the virus prevent serious illness caused by newly emerging variants? A team led by physician Michel Nussenzweig from Rockefeller University in New York took a closer look: The third vaccination therefore means that the immune system can produce a wider range of antibodies – including those that fight omicrons. The researchers published their results in the journal Nature.

Nussenzweig and his colleagues analyzed blood samples from 42 people aged 23 to 78 who had received three doses of an mRNA vaccine (8 with Moderna, 34 with Biontech/Pfizer). The samples were taken after the first, second and third dose. None of the study participants had been infected with Sars-CoV-2 before vaccination. The authors examined memory B cells in their analysis. So far, these cells have been less researched in this context, the focus has been primarily on the cytotoxic T cells.

These T cells recognize and kill the body’s own cells that have been infected by viruses. The B memory cells, on the other hand, represent a kind of immune reserve. They arise during a vaccination or infection in parallel with the plasma cells that produce antibodies. Their genome encodes the same recognition sequences as the plasma cells, but they do not produce any antibodies themselves, so they remain in the body for a very long time. Under certain conditions, such as in the course of a breakthrough infection, they multiply and, among other things, generate new plasma cells that produce antibodies against the pathogen.

Greater bandwidth and increased effectiveness against omicron

Nussenzweig’s working group has now established that the number of memory B cells increased after the third dose compared to the second. The antibodies produced also had a greater breadth and effectiveness in neutralizing Sars-CoV-2 than those that arose after a second vaccination. The authors of the study attribute this to the fact that antibodies from new memory B cells attack more areas of the virus’s receptor-binding domain, which is important for the infection, than the antibodies formed after the second dose. However, they add that even a third vaccination cannot always prevent the infection from breaking out.



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