Use of an individual-based model of pneumococcal carriage for planning a randomized trial of a whole-cell vaccine
Fig 2
Prevalence and sample size over the follow-up period in the higher transmission setting.
Panels are organized column-wise by vaccine efficacy: 3 colonization equivalents (c.e.), or 26% reduction in carriage duration (A, D); 5 c.e., or 39% (B, E); and 10 c.e., or 63% (C, F). Within each panel, results are presented separately for infants (blue) and toddlers (purple). (A-C) The joint kernel density estimate (see Methods) of the control and vaccine arm prevalences at each sampling time (every 3 months until 24 months post-vaccination) is shown as a contour map truncated by the convex hull of the simulated points, with the median values marked by a cross. These crosses are connected chronologically, and those corresponding to 0, 12, and 24 months post-vaccination are labeled. The dashed line indicates equal prevalences in the two arms. (D-F) The kernel density estimate of the total sample size (combined size of both samples) needed to detect a difference between control and vaccine arm prevalences at each sampling time (assuming 80% power, 5% type I error rate, balanced arms). The horizontal bars in each violin plot indicate the minimum, median, and maximum values across all simulations. In (D), the maximum sample sizes for infants and for toddlers at 3 months post-vaccination are greater than one million (236 million and 4 million, respectively) and outside the limits of the y-axis.