Lymph Node Aspiration to Decipher the Immune Response of Beta-variant Recombinant Protein Booster Vaccine (VidPrevtyn Beta, Sanofi) Compared to a Bivalent mRNA Vaccine (Comirnaty Original/Omicron BA.4-5, BioNTech-Pfizer) in Adults Previously Vaccinated With at Least 3 Doses of COVID-19 mRNA Vaccine.

In order to investigate whether a germinal center response occurs following vaccine boost and to characterize it based on the type of vaccine received, we aim to analyze Spike and/or RBD-specific germinal center B cells within the draining lymph nodes. To achieve this, we will perform lymph node fine needle aspiration of the draining lymph node in 6 subjects in each study arm, 3 to 6 weeks after the booster vaccine injection.