Dynamics of B-Cell Responses after SARS-CoV-2 Vaccination in Spain.

The high mortality rate due to COVID-19 has necessitated the mass vaccination against SARS-CoV-2 to induce protective humoral and cellular immunity. (1) Objective: To study the dynamics of SARS-CoV-2-specific B cells after two doses of the Pfizer-BioNTech SARS-CoV-2 vaccine. (2) Methods: Immunophenotyping and cellular cultures were used to determine the kinetics of B-cell subpopulations and vaccine responses in volunteers before and seven days, three months and seven months after the second dose in Spain (n = 19). (3) Results: Seven days after immunisation, memory B cells and plasmablasts expressing receptors for factors implicated in the maturation of plasma cells were augmented in blood. Three months after vaccination, SARS-CoV-2 spike-specific plasmablasts disappeared from circulation while spike-specific memory-B cells circulated, with heterogeneous dynamics among individuals. (4) Conclusion: After vaccination, specific plasmablasts equipped with receptors for maturation factors were quickly generated and disappeared rapidly from the blood, while specific memory B cells circulated for at least seven months.