Great question. Isn't the reason the delta variant is so effective at infecting (mildly) already vaccinated people due to the fact that the immune system (unex

Great question. Isn't the reason the delta variant is so effective at infecting (mildly) already vaccinated people due to the fact that the immune system (unexpectedly) doesn't produce antibodies for the broad structures in the spike protein? My understanding based on a few papers I've read is that the immune system was more efficient than anticipated, and tended to produce antibodies based on specific structures that are part of the spike protein. Apparently, evolving an entirely new spike protein would be implausible, but mutations on the existing spike protein are more frequent, and this narrower than expected antibody is slower to bind to these.