New analyses of data from the RCT in young adults
REGRESSION, DISEASE
For a detailed description of the trial, please see supplementary material. We reanalysed the serological results of IgG anti–Pre-vaccination (baseline, day 0) and post-vaccination (day 17 [range, 14–23] and day 137 [range, 97–170]) sera were obtained and tested using ELISA as described [The results were expressed as endpoint titres; geometric mean titres (GMTs) and ≥4-fold increases in titre post-vaccination over baseline were calculated [Serum bactericidal activity (SBA) was examined in 20 remaining archived sera of vaccinees on day 17 post-vaccination as described [We estimated the potential threshold of serum IgG anti–The primary analysis included bivariate and multivariable logistic regression models to assess the Prentice criteria for a valid immunological substitute endpoint [Sera on day 17 post-vaccination were obtained from 371 of 450 (82%) participants. Therefore, we employed the predictive mean matching multiple imputation method using the observed information on vaccination status and baseline serum IgG anti–Mantel-Haenszel analysis was employed to examine the effect of vaccination on disease in stratification by levels of antibodies ≥1:1600 or <1:1600, 17 days post-vaccination.We also used the method developed by Siber et al. [The VEConsistency between VEWe also used a nonparametric method [Data were analysed using the SPSS Statistics, version 28 (IBM Corp., Armonk, NY, USA), SAS Software, version 9.4 (SAS Institute Inc., Cary, NC, USA), and R version 4.1.0 (The R Foundation for Statistical Computing, Vienna, Austria).