Fig. 2: Prediction results.

Prediction results from fitting the best-fit model to three selected participants from Keio University Hospital. The area to the right of the vertical reference line displays the predicted results. Data and predicted results of antibody titers (anti-receptor-binding domain IgG) for a participant whose antibody titer increased to approximately 2500 BAU/mL (a) and 3500 BAU/mL (b) after two vaccination doses. c Data and predicted results for a participant with only one measurement available (week 3) owing to missing data. Time instants are shown when the lower limit of the 95% prediction interval and the median value falls below the 154 BAU/mL threshold, the horizontal reference line, for classification as a protective antibody titer. The vertical axis represents the logarithmic scale.