The immune response being focused now, due to the vaccine breakthrough infection, will now focus on other domains of the spike protein.
Some of these domains are more conserved (people who had breakthrough infections were doing fantastic because they got broadly neutralizing antibodies which declined rapidly but their broadly neutralizing antibodies had been directed against the more conserved domains of spike protein).
`Conserved domain - very important, evolutionarily speaking - Virus wouldn't benefit from differentiation such as to allow the immune system to recognize its domains. The more it is conserved (less immunogenic), and the more closely it resembles peptides of our own cells (immune refocusing refocuses the immune system to make it concentrate on domains of spike protein that resemble our self components.)
The more the domain is conserved, and the lower the immunogenicity.
We start to induce immune responses that can recognize self-components in our cels.
`So if you create an antibody