Antispike response by risk factors associated with immunization after 2 vaccine doses. Serologic response to a 2-dose vaccination according to main factors associated with immunization after dose 2 (identified in multivariate analysis; see text and supplemental Tables 3 and 4). (A) Antispike antibody level. The violin plots contain interior box plots with upper and lower horizontal edges the 25th and 75th percentiles of antibody level and middle line the 50th percentile. The shape of the violin plots shows the smoothed probability density of the data. (B) Proportion of detectable antispike antibodies with 95% CI. The positivity threshold was given by the manufacturer for each used serological assay as detailed in supplemental Materials.