Booster Immunization Improves Memory B Cell Responses in Older Adults Unresponsive to Primary SARS-CoV-2 Immunization
Marije K. Verheul, Kim H. Nijhof, Mary‐lène de Zeeuw‐Brouwer, Geraly Duijm, Hinke ten Hulscher, Lia de Rond, Lisa Beckers, Dirk Eggink, Sophie van Tol, Johan Reimerink, Mardi C. Boer, Josine van Beek, Nynke Y. Rots, Rob van Binnendijk, Anne‐Marie Buisman
Abstract
The generation of a specific long-term immune response to SARS-CoV-2 is considered important for protection against COVID-19 infection and disease. Memory B cells, responsible for the generation of antibody-producing plasmablasts upon a new antigen encounter, play an important role in this process. Therefore, the induction of memory B cell responses after primary and booster SARS-CoV-2 immunizations was investigated in the general population with an emphasis on older adults. Participants, 20-99 years of age, due to receive the mRNA-1273 or BNT162b2 SARS-CoV-2 vaccine were included in the current study. Specific memory B cells were determined by ex vivo ELISpot assays. In a subset of participants, antibody levels, avidity, and virus neutralization capacity were compared to memory B cell responses. Memory B cells specific for both Spike S1 and receptor-binding domain (RBD) were detected in the majority of participants following the primary immunization series. However, a proportion of predominantly older adults showed low frequencies of specific memory B cells. Booster vaccination resulted in a large increase in the frequencies of S1- and RBD-specific memory B cells also for those in which low memory B cell frequencies were detected after the primary series. These data show that booster immunization is important for the generation of a memory B cell response, as a subset of older adults shows a suboptimal response to the primary SARS-CoV-2 immunization series. It is anticipated that these memory B cells will play a significant role in the immune response following viral re-exposure.