Figure 1. Concentrations of total binding antibodies in serum to spike RBD following two and three COVID-19 vaccine doses.

Panel A: Binding antibody responses to the SARS-CoV-2 spike RBD in serum at one, three and six months following the second dose, and one month following the third vaccine dose, in PLWH (orange) and controls (blue) who were COVID-19 naive at the studied time point, as well as individuals who had recovered from COVID-19 at the studied time point (COVID group, black). Participants who experienced a post-vaccination infection were relocated from their original group into the COVID group at their first post-infection study visit, where they are denoted by a red symbol. Participant Ns are shown at the bottom of the plot. The thick horizontal red bar represents the median; thinner horizontal red bars represent the IQR. P-values were computed using the Mann-Whitney U-test (for comparisons between groups) or the Wilcoxon matched pairs test (for comparisons across time points within a group) and are uncorrected for multiple comparisons. ULOQ: upper limit of quantification; LLOD: lower limit of detection. Panel B: Temporal declines in serum binding antibody responses to spike-RBD following two vaccine doses in PLWH (orange) and controls (blue) who remained COVID-19 naive during this period. Only participants with a complete longitudinal data series with no values above the ULOQ are shown. Panel C: Binding antibody half-lives following two COVID-19 vaccine doses, calculated by fitting an exponential curve to the data shown in panel B. Ns are indicated at the bottom of the plot. Red bars and whiskers represent the median and IQR. P-value computed using the Mann Whitney U-test.