B-cells in bone marrow up to 11 months after first Covid infection. That's not a novel finding, it is the way the immune system is intended to function.

The barrier to long-term immunity is the relative rapidity with which Covid-19 spreads and the quick rise of variant strains. B-Cells produce antibodies that are intended to lock onto a very specific confirmation of a very specific protein. They are fantastic at identifying the presence of that specific protein region, but not great at finding anything else. If a mutation arises that changes the recognized site enough, your antibodies will still protect you against the previously encountered strain, but may be useless against a different strain.

We see a similar issue with Influenza. This is why a flu shot is suggested every year. Receiving the flu shot introduces you to new strains as well as boosting memory immune response against previously encountered strains. The best course of action for everyone, is still to get vaccinated if possible, to reduce the number of vectors for mutation to arise in.
[Post edited by Maupin233 at 05/26/2021 2:26PM]