Sci. Immunol. https://doi.org/10.1126/sciimmunol.abi6950 (2021).

The induction of memory B cells by mRNA vaccines remains poorly understood. In Science Immunology, Wherry and colleagues assess circulating antibodies and antigen-specific memory B cells over the course of first and second immunizations in a cohort of 33 individuals who were SARS-CoV-2 naive and 11 individuals who had recovered from SARS-CoV-2 infection. In SARS-CoV-2-experienced individuals, the first dose induces a response similar to that induced by the boost dose in naive individuals by significantly increasing the amount of spike- and RBD-specific antibodies as compared to pre-existing or first-dose levels and by inducing a robust increase in neutralization. In naive individuals, the first dose induces and the second dose expands spike- and RBD-specific memory B cells, while in SARS-CoV-2-recovered individuals, the first dose robustly expands pre-existing memory B cells, with no additional boosting after the second dose. The baseline for antigen-specific memory B cells in recovered individuals correlates with the antibody response post-first dose, indicating that memory B cells are the major contributors to antibody recall responses post-vaccination.