Primary seroprotection response was defined as antibody titer against hepatitis B surface antigen (anti-HBs) ≥10 mIU/mL at 8 weeks after 2-dose vaccination series and at 4 weeks after 3-dose vaccination series. If the completion of the vaccine series was delayed (a delay of ≤4 weeks was allowed), the trial protocol specified obtaining an antibody result at 8 weeks for the 2-dose series or at 4 weeks for the 3-dose series after vaccine completion for use in the primary outcome analysis. The study was designed separately for the two study populations (Groups A and B), and the analysis was conducted separately, as prespecified in the study protocol and Statistical Analysis Plan (SAP). In Group A, two-sided 97.5% confidence intervals (CI) were specified for the SPR differences between study arms (presented in the Statistical Analyses sections below). In Group B, two-sided 95% Wilson CI around the single-arm estimate was specified (presented in the Data Table below).

The protocol required reporting of (1) Grade ≥2 AEs, (2) AEs that led to a change in study treatment regardless of grade, (3) AEs meeting serious AE (SAE) definition or expedited AE (EAE) reporting requirement, (4) Grade ≥1 local and systemic injection reactions within 7 days of any study vaccine injection, (5) medically attended adverse events (MAAE) regardless of grade, and (6) potential immune-mediated AEs regardless of grade. Grading was per DAIDS AE Grading Table (Version 2.1): Grade 1 (mild), 2 (moderate), 3 (severe), 4 (life-threatening) and 5 (death). DAIDS EAE Manual (V1.0) was used. Wilson method was used for confidence intervals.