Neutralizing antibody titers against BA.5, WT, or XBB.1.9.1 in individuals vaccinated with zero, one, two, and three doses. (A) NAb titers against BA.5, wild-type, or XBB.1.9.1 were measured in individuals who had received zero, one, two, or three doses of the COVID-19 vaccine and had no prior SARS-CoV-2 infections. (B) NAb titers against BA.5, WT, or XBB.1.9.1 were assessed in individuals who had received zero, one, two, or three doses of the COVID-19 vaccine 20–50 days after being infected with the BA.5 variant. (C) NAb titers against BA.5, WT, or XBB.1.9.1 were assessed in individuals who had received zero, one, two, or three doses of the COVID-19 vaccine 3 months after being infected with the BA.5 variant. The NAb titers in each group are presented as geometric mean titers at the top of each panel. Significance was determined using Mann-Whitney U tests (*P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001; and n.s., not significant.).