Immune memory is the mechanism that protects us against re-infection by pathogens. The success of vaccines is based on this defense strategy that consists in the production of blood antibodies and of memory B cells, able to reactivate into antibody-secreting cells upon a new infection. The team led by M. Mahévas, J.-C. Weill and C.-A. Reynaud has followed memory B cells in two cohorts of patients with mild or severe SARS-Cov-2 infection over 6 months, in collaboration with the team of F. Rey at Pasteur Institute. They show that memory B cells persist and even improve their recognition of the spike protein virus-binding domain over time, as well as their production of neutralizing antibodies. These encouraging results suggest moreover that the broad recognition potential of memory B cells and their capacity for selective proliferation may allow them to adapt to some virus variants and generate a still effective response upon a drifted virus challenge (Sokal, Chappert et al., Cell, February, 2021).