The team of Matthieu Mahévas and Pascal Chappert have been following up on their recent work on B cell responses in the context of SARS-CoV-2 infection and mRNA vaccination. Studying memory B cells and plasma cells post SARS-CoV-2 Omicron BA.1 breakthrough infection in individuals previously vaccinated with three doses of the COVID-19 mRNA vaccine, they show clear signs of antigen imprinting from the Hu-1 Spike encoded in the vaccine. However, the diversity of the vaccine-induced memory B cell repertoire and the possibility to further mature such memory through clonal hierarchy reorganization and additional rounds of affinity maturation combined to induce an adaptation to the new viral strain and a marked improvement in overall neutralizing breadth and potency post-infection. These findings have fundamental implications for the design of future vaccination booster strategies.