The findings add to growing evidence that most immunized people with mRNA vaccines They may not need a booster until the virus and its variants have grown beyond their current forms, which is not guaranteed. It is possible that People who have previously recovered from COVID-19 If they are vaccinated they don’t need it reinforcement Even if the virus undergoes a significant transformation.
“It’s a good indication of how sustainable it is. Our immunity from this vaccineAli Elebedy, an immunologist at Washington University in St. Louis, who led the study, published in the journal Nature.
The study did not include a vaccine made by Johnson & Johnson, although Dr. Elebedi said he expects the immune response to be less durable than that produced by messenger RNA vaccines.
Elebedi and his colleagues reported last month that in people who survive COVID-19, the immune cells that recognize the virus dormant in the bone marrow For at least eight months after infection. A study by another team indicated that so-called memory B cells continue to mature and strengthen for at least a year after infection.
Based on those findings, the researchers suggested that immunity could last for years and perhaps a lifetime in people who contracted the coronavirus and were subsequently vaccinated. But it was not very clear whether such a long-lasting effect could be achieved by vaccination alone.
Elebedi’s team sought to answer that question by investigating the source of memory cells: the lymph nodes, where immune cells are trained to recognize and fight viruses.
After an infection or vaccination, a special structure called the germinal center forms in the lymph nodes. This structure is a kind of elite school for B cells, a training ground where they become increasingly sophisticated and learn to recognize a diverse set of viral genetic sequences.
These cells are more likely to thwart emerging virus forms if they have more time and range to practice.
“Everyone is always focused on the development of the virus; This suggests that B cells are doing the same thing,” said Marion Pepper, an immunologist at the University of Washington in Seattle. “And it’s protecting against the ongoing evolution of the virus, which is really encouraging.”
After contracting the coronavirus, the germinal center forms in the lungs. But after vaccination, the learning of cells occurs in adjacent lymph nodes, within the reach of researchers.
Elebedy and his colleagues recruited 41 people, including eight with a history of virus infection, who were immunized with two doses of the Pfizer-BioNTech vaccine. From 14 of these people, the team took lymph node samples three, four, five, seven and 15 weeks after the first dose.
Yale immunologist Akiko Iwasaki said this painstaking work makes it a “heroic study.” “It’s very difficult to do this kind of careful time series analysis in humans.”
Elebedi’s team found that 15 weeks after receiving the first dose of the vaccine, the germinal center was still highly active in all 14 participants and the number of memory cells capable of recognizing the coronavirus had not decreased.
“That’s a very good sign that reactions will continue for about four months after vaccination,” said Elebedi. The germinal centers are usually at their highest expression one to two weeks after vaccination and then decline.
“Usually after four to six weeks there isn’t much left,” said Deepta Bhattacharya, an immunologist at the University of Arizona. But the germ centers induced by mRNA vaccines “stay active for months and do not degrade much in most people.”
Bhattacharya said much of what scientists know about the persistence of germ centers comes from animal research. The new study is the first to show what happens to people after vaccination.
The results suggest that a large proportion of those vaccinated will be protected in the long run, at least against existing coronavirus variants. But older adults, people with weakened immune systems, and those taking immunosuppressant drugs may need a booster. People who survived COVID-19 and were later immunized may never need them.
It is difficult to predict how long the protection of messenger RNA vaccines will last. If there were no types of bypassing immunity, it could theoretically last a lifetime. But the virus apparently continues to evolve.
“Any need for a booster would be due to variation, not a drop in immunity,” Bhattacharya said. “I don’t see that happening.”
People who were infected with the coronavirus and were then vaccinated experienced a significant increase in their antibody levels, most likely because their memory B cells, which produce antibodies, took several months to develop before vaccination. Took it.
The good news: The booster shot will likely have the same effect as previous infections in immunized people, Elebedy said. “If you give them one more chance to participate, they will respond in a big way,” he said, referring to memory B cells.
When it comes to boosting the immune system, vaccination is “probably better” than recovering from an actual infection, he said. Other studies have suggested that the performance of memory B cells generated after vaccination is more diverse than that generated by infection, suggesting that vaccines protect against variants better than natural immunity alone.
Elebedy said the results also suggest signs of a persistent immune response produced by mRNA vaccines rather than by conventional ones like Johnson & Johnson.
But it’s an unfair comparison, because Johnson & Johnson’s vaccine is given in a single dose, Iwasaki said: “It’s likely that if J&J had a second dose, it could have inspired a similar reaction.” “
Apoorva Mandavilli is a reporter for the Times and focuses on science and global health. In 2019 he won the Victor Kohn Award for Excellence in Medical Science Reporting. @apoorva_nyc