A phenomenon called 'original antigenic sin' describes a situation where exposure to a modified vaccine strain results in which outcome?

Correct answer: The immune system favors antibodies against the original strain rather than new variants

Original antigenic sin occurs when the immune system relies on its existing memory cells from an encounter with a historical strain of a virus, rather than mounting a fresh response to altered epitopes on a new vaccine variant. This can blunt the effectiveness of updated booster shots, as the body expends energy making mismatched antibodies from old templates.