The research team that previously discovered spike-resistant plasma cells in the bone marrow of people who recovered from the novel coronavirus has now taken cell samples from the lymph nodes of the vaccinated person (Pfizer). They discovered that the B cells in the lymph nodes are undergoing a process called somatic hypermutation. This can adjust the antibodies produced by the B cells to better bind to the spike protein. They found that this process lasts for at least 15 weeks after the first injection, which means that the immune system attaches great importance to the spike protein and tries to produce the best antibodies to fight it.
This is not surprising, because we have seen that over time, the antibodies produced improve in neutralizing the virus. We have also seen that some people retain antibodies for almost a year after being vaccinated, but if you do not get a full immune response, this will not happen.
However, the person in charge of this research group told the media that this result means that booster injections may not be needed. I don't think the data tells us this at all.
Given this powerful immune response, if you are fully vaccinated and respond to the vaccine, even if your antibodies disappear completely, you may have memory B and T cells for decades, perhaps for the rest of your life. If infected with the new coronavirus in the future, they will produce antibodies and T cells much faster than people who have never been vaccinated (days instead of weeks). But memory B and T cells cannot prevent the occurrence of infections. They can only react to eliminate the infection.
If we want to end the pandemic, we need a large number of people with enough antibodies to prevent infection and break the chain of transmission. A person who has been vaccinated against a breakthrough infection is about half as likely to transmit the virus to another person, at least for the alpha variant. But delta variants are easier to spread, even for alpha variants, once the antibodies start to wear off we can see an increase in cases.
On a personal level, progressive infections are less serious, but for some people they are still unpleasant. And we still do not have data on the advance infection of Covid in the medium and long term.
https://www.nature.com/articles/s41586-021-03738-2_reference.pdf