That painstaking work makes this a “heroic study,” said Akiko Iwasaki, an immunologist at Yale. “This kind of careful time-course analysis in humans is very difficult to do.”
Dr. Ellebedy’s team found that 15 weeks after the first dose of vaccine, the germinal center was still highly active in all 14 of the participants, and that the number of memory cells that recognized the coronavirus had not declined.
“The fact that the reactions continued for almost four months after vaccination — that’s a very, very good sign,” Dr. Ellebedy said. Germinal centers typically peak one to two weeks after immunization, and then wane.
“Usually by four to six weeks, there’s not much left,” said Deepta Bhattacharya, an immunologist at the University of Arizona. But germinal centers stimulated by the mRNA vaccines are “still going, months into it, and not a lot of decline in most people.”