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Distributions of the total trial duration for trials with (a) 2, (b) 3, and (c) 4 study groups, all with one placebo group. (a) 1 vaccine regimen versus placebo. (b) 2 vaccine regimens versus placebo. (c) 3 vaccine regimens versus placebo. For trials with multiple vaccine groups, a trial completes once all of the vaccine groups reach the end of evaluation. The calculations for this figure assume the true VE(0-18) is constant over time.
