PMC9020769_01
SARS-CoV-2 antibody responses and specific memory B cells. (A) Anti-Trimeric Spike specific IgG, total anti-RBD antibody levels and (B) percentage of S+ (low-affinity) and S++ (high-affinity) MBCs measured at different time points in vaccinated HCWs (in blue; n=16) and in the patient (in red): 3 weeks and 3 months after the second dose and 10 days post-booster (BNT162b2 mRNA vaccine for control HCWs and Ad26.COV2.S COVID-19 vaccine for the patient). Column indicate mean and SEM. Statistical significance was determined using Wilcoxon matched pairs signed rank test. **p < 0.01, ***p < 0.001, ****p < 0.0001.
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Repeated serum antibody measurements showed a minimal response to the BNT162b2 mRNA vaccine as compared to healthy control HCWs ( Figure 1A ). Total anti-RBD antibodies were 23.1 BAU/ml three weeks after completion of vaccine cycle and 93.9 BAU/mL after three months, both values being much lower than those of the controls (control HCWs medians: 1717 BAU/mL (IQR: 1174-3044) at three weeks; 655 BAU/mL (IQR: 463.8-1156) at three months,  Figure 1A ). Three months after vaccination, the frequency of S+ MBCs decreased to 0.11% (IQR: 0.09-0.18) ( Figure 1B ). Three months after the 2nd dose, the median value of S++ MBCs was 0.09% (IQR 0.05-0.23) ( Figure 1B ).