[erhk]

If you trigger a memory response why would it matter if it was recalling a different similar protein? Wouldnt your immune system also remember and respond to a real pathogen, suggesting that the orginal vaccine was sufficient? In what world do you identify a pathogen but the fail to respond to it? Its not as if your body responds significantly differently to distinct illnesses.

Perhaps my understanding here is too cursory but this claim is pretty extraordinary for what I know.

[TheBlight]

Your immune response can be triggered by a specific epitope but provide a less than optimal response. I'm not pulling this out of my ass. Moderna tried making a beta strain specific booster but noticed the original wild strain antibodies elicited from previous vaccination were activated. See also: https://www.cell.com/trends/immunology/fulltext/S1471-4906(2...

I suspect this is part of the reason why we never saw an "update" for the delta variant.

[erhk]

What is a less than optimal response? Partial binding?

[TheBlight]

Bind but not neutralize.