Figure 2 (A) Increase of Delta (δ)- and Omicron (ο)- BA.1/BA.2 neutralizing antibody (NA) titers after mRNA booster in age- and gender-matched individuals pre-vaccinated with AZD/mRNA (N=5), AZD/AZD (N=5), and mRNA/mRNA (N=5). δ- and ο-BA.1/BA.2-NA titers after BA.1 (breakthrough) infection in triple-vaccinated and unvaccinated individuals. (B, C) δ- and ο-BA.1 NA titers and CD4+ or CD4/CD8+ T-cell reactivities before/after BA.1 (breakthrough) infection. Geometric mean titers (GMT), prevalence of NAs >1:10 or number of individuals tested are tabulated. ****: p < 0.0001; ***: p < 0.001 **: p < 0.01; * p < 0.05. Horizontal dashed lines indicate test cut-off values.