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The SARS-CoV-2 Omicron variant can escape neutralization by vaccine-elicited and convalescent antibodies. Memory B cells (MBCs) represent another layer of protection against SARS-CoV-2, as they persist after infection and vaccination and improve their affinity. Whether MBCs elicited by mRNA vaccines can recognize the Omicron variant remains unclear. We assessed the affinity and neutralization potency against the Omicron variant of several hundred naturally expressed MBC-derived monoclonal IgG antibodies from vaccinated COVID-19-recovered and -naive individuals. Compared with other variants of concern, Omicron evaded recognition by a larger proportion of MBC-derived antibodies, with only 30% retaining high affinity against the Omicron RBD, and the reduction in neutralization potency was even more pronounced. Nonetheless, neutralizing MBC clones could be found in all the analyzed individuals. Therefore, despite the strong immune escape potential of the Omicron variant, these results suggest that the MBC repertoire generated by mRNA vaccines still provides some protection against the Omicron variant in vaccinated individuals., Competing Interests: Declaration of interests Outside of the submitted work, M. Mahévas received research funds from GSK and personal fees from LFB and Amgen. J.-C.W. received consulting fees from Institut Mérieux. P.B. received consulting fees from Regeneron Pharmaceuticals. J.-M.P. received personal fees from Abbvie, Gilead, Merck, and Siemens Healthcare. F.A.R. is a member of the board of MELETIOS Therapeutics and of the Scientific Advisory Board of eureKARE., (Copyright © 2022. Published by Elsevier Inc.)

In addition to serum immunoglobulins, memory B cell (MBC) generation against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is another layer of immune protection, but the quality of MBC responses in naive and coronavirus disease 2019 (COVID-19)-recovered individuals after vaccination remains ill defined. We studied longitudinal cohorts of naive and disease-recovered individuals for up to 2 months after SARS-CoV-2 mRNA vaccination. We assessed the quality of the memory response by analysis of antibody repertoires, affinity, and neutralization against variants of concern (VOCs) using unbiased cultures of 2,452 MBCs. Upon boosting, the MBC pool of recovered individuals expanded selectively, matured further, and harbored potent neutralizers against VOCs. Although naive individuals had weaker neutralizing serum responses, half of their RBD-specific MBCs displayed high affinity toward multiple VOCs, including delta (B.1.617.2), and one-third retained neutralizing potency against beta (B.1.351). Our data suggest that an additional challenge in naive vaccinees could recall such affinity-matured MBCs and allow them to respond efficiently to VOCs., Competing Interests: Declaration of interests Outside of the submitted work, M. Mahévas. received research funds from GSK and personal fees from LFB and Amgen. J.-C.W. received consulting fees from Institut Mérieux. P.B. received consulting fees from Regeneron Pharmaceuticals. J.-M.P. received personal fees from Abbvie, Gilead, Merck, and Siemens Healthcare. F.R. is a member of the board of MELETIOS Therapeutics and of the Scientific Advisory Board of eureKARE., (Copyright © 2021. Published by Elsevier Inc.)