system
Given the following post, respond as if you're commenting on Reddit:
human
Does antibody response adapt with exposure to different Covid strains?

If you recieved a Covid-19 vaccine, the vaccine generated antibody and T-cells to equip the immune system to respond to the alpha Covid-19 virus. In the case of the mRNA vaccines, it was really primed just toward the spike protein. If you are vaccinated and are exposed to a variant such as Delta, I understand that current vaccines have a high probability of attenuating illness. When this occurs, does your antibody response further adapt to be more efficient in warding off that variant in future exposures, or if it is good enough to work, does it remain unchanged? What exactly does or does not change?
gpt
Yes, to an extent.

If you have pre-existing memory B cells (which can be stimulated to make antibodies of a specific type), and you're exposed to a variant strain, you can get antibodies to the new strain in two different ways. 

One, you can start with brand-new B cells, starting from scratch as if you'd never had any exposure. Two, you can adapt the pre-existing B cells to better fit the new variant.

B cells can do the adaptation because of a phenomenon called "somatic hypermutation", in which the genomic regions that make the antibodies are rapidly mutated. Most of the outcomes of these mutations are bad (non-functional antibodies, or less-functional antibodies) but the small number that fortuitously bind better to the antigen are selected and amplified and can eventually dominate the immune response.

This adaptation process probably is most important when the antigen changes are fairly minor, which is the case with all the COVID variants so far. In these cases, the original antibodies still do bind, just less strongly, so there's room for adaptation and improvement.

If the changes are more drastic, and you extensively lose binding, then starting from scratch may be more likely.

All this is wildly oversimplified, of course.