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Memory B cells become increasingly complex over time and learn to recognize various viral genetic sequences. The longer they have to practice, the wider the virus variants they can block.

Researchers showed last year that the elite school within the lymph nodes, in which B cells, called the germinal center, are trained, remains. active for at least 15 weeks After the second dose of the Covid vaccine. In an updated study published in the journal NatureThe same team showed that six months after vaccination, memory B cells continue to mature and the antibodies they produce continue to gain the ability to recognize new variants.

“These antibodies at six months are better binders and stronger neutralizers than those produced one month after vaccination,” said immunologist Ali Ellebedy of the University of Washington in St.

In the most recent study, another team showed that the third shot created a richer pool of B cells than the second shot, and that the antibodies they produced recognized a wider range of variants. In laboratory experiments, these antibodies were able to fend off the Beta, Delta, and Omicron variants. In fact, the study found that more than half of the antibodies seen one month after the third dose were able to neutralize Omicron, although the vaccine was not designed for this variant.

“If you took a third dose, you would get a rapid response that would have quite a lot of specificity for Omicron, which explains why people who took the third dose did so much better,” said Michel Nussenzweig. , an immunologist at Rockefeller University who led the study.

Memory cells produced after infection with the coronavirus rather than vaccines appear to be less effective against the Omicron variant. according to a research It was published last month in Nature Medicine. “While the immunity generated by infection is highly variable, the vaccine response is much more consistently good,” said Marcus Buggert, an immunologist at the Karolinska Institutet in Sweden, who led the study.

Dr. Buggert said that while most people, whether vaccinated or not, show only a small decrease in T-cell response to Omicron, about one-fifth show “significant reductions in their response,” by about 60 percent. He said the differences are most likely due to their underlying genetic makeup.