Fig. 1

Distribution of anti-spike receptor-binding domain IgG titer (in natural logarithmic scale) by history of COVID-19 diagnosis and vaccination status. Group 1: history of COVID-19 diagnosis, complete vaccination; Group 2: history of COVID-19 diagnosis, incomplete vaccination; Group 3: no history of COVID-19 diagnosis, complete vaccination; Group 4: no history of COVID-19 diagnosis, incomplete vaccination, thick dot and whiskers denote group mean ± SD. *** Denotes significant difference between groups with p < 0.001