Figure 5.

Estimates and type I error by basic reproduction number, R₀, and model for an analysis of vaccine efficacy (VE) in an outbreak setting for direct VE of 0. Median VE estimate (A) and empirical type I error (B) for direct VE of 0 (horizontal line in (A)) versus R₀, for individually randomized trial (IRT) analyzed with stratified Cox model (squares, solid line), cluster-randomized trial (CRT) analyzed with a Cox model with a gamma-distributed shared frailty (circles, dashed line), and stepped wedge trials with 4 clusters crossing over every 28 days (SWT-A, filled points) and with 1 cluster crossing over every 7 days (SWT-B, unfilled points) analyzed by a Cox model with a gamma-distributed shared frailty (SWT-PH; diamonds, dotted line), nonparametric within-period method weighted across periods by total case count (NPWP-2; upward triangle, dash-dotted line), and synthetic control method equally weighted across clusters and weighted across periods by total case count (SC-2; downward triangle, long-dash line). The horizontal line in (B) denotes the nominal type I error of 5%.