Figure 5.

Vaccination with Original Strain antigen induces an omicron-specific antibody response and comparable B- and T-cell responses to the original and Omicron Spike protein. Anti-SARS-CoV-2 Omicron B1.1.529 antibodies were measured before and after completion of the primary vaccination series in participants without evidence of a previous infection (n = 12) (A). Specific memory B cells targeting the original Spike S1 or Omicron BA.1 Spike S1 were investigated using B cell ELISpot for participants who were vaccinated without prior infection (B), vaccinated after a prior infection (C), or only infected without a vaccination (D). IFN-γ-producing cells among PBMCs cultured in the presence of overlapping peptides of the Spike antigen from SARS-CoV-2 Original Strain or Omicron are expressed as spot forming units (SFU) (E–G). Graphs show SFU of IFNγ spots per 2x10⁵ PBMC after vaccination in participants without (E) or with SARS-CoV-2 infection (F) prior to vaccination, or in previously infected children before their first vaccination (G). Statistical significance of differences was analyzed by a paired Wilcoxon test. ns, not significant; ****, p < 0.0001.