Antibody response after a third dose of SARS-CoV-2 vaccine. Antibody response before and after the third dose (D3). (A) Antibody levels (in BAU/mL) after the second and third dose of vaccine. Dots represent individual values and are filled according to the response after dose 2 (red for no response and blue for response weak response [<50 BAU/mL]). Antibody level significantly increased after dose 3 (P < .001, Mann-Whitney U test). (B-C) Antibody qualitative response to the third dose classified according antibody levels among patients with no (B) or weak (C) prior detectable response. “No” for undetectable response, “weak” for response <50 BAU/mL, and “good” for response ≥250 BAU/mL. The positivity threshold was given by the manufacturer for each used serological assay as detailed in supplemental Materials. D2, dose 2.