Design questions for Streptococcus pneumoniae vaccine trials with a colonisation endpoint

Abstract

Evaluation of vaccine efficacy for protection against colonisation (VEcol) with Streptococcus pneumoniae and other bacterial pathogens is often based on a cross-sectional study design, in which only one nasopharyngeal sample is obtained per study subject. Here we investigate the feasibility of this study design by investigating a number of practical design problems. Specific questions are related to the timing of colonisation measurement with respect to the time of vaccination, the adjustment for the within-host replacement of vaccine-type colonisation by the non-vaccine type pneumococci, and the impact of multiple serotype colonisation on VEcol estimation. We also discuss the issue of choos..