Fig. 2
Change in the neutralizing and spike antibody titers in individuals who experienced breakthrough infection, received the booster vaccine, or were unboosted during follow-up
Shown are NAb titers against the original Wild-type strain (A), the Delta variant (B), and the Omicron BA.1 variant (C) determined by 50% focus reduction neutralization test (FRNT50) using the serum at baseline and follow-up. Also shown are anti-spike antibody titers measured with the Abbott reagent (D) and the Roche reagent (E) at baseline and follow-up. Box plots show the median, interquartile range, and full range. The dushed horizontal lines indicate the LOD in the present analysis (NT50 < 40 in FRNT50 and U/mL > 25,000 in Roche assay)
The fold-change values are estimated ratios of geometric means for antibody titers based on the GEE model (ns: not significant; *P < 0.05; **P < 0.01; ***P < 0.001)
Abbreviations: AU, arbitrary units; B, baseline; F, follow-up; GEE, generalized estimating equation; LOD, limits of detection; NT50, 50% neutralization titer; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.