Sample size calculation
SECONDARY
Sample size calculation was primarily based on the possibility to evaluate the secondary efficacy objective. In the placebo group, vaccine-preventable outcome incidence was assumed at 5% and protective efficacy at 75%. With 80% power and a significance level of 5%, 337 participants per group would be needed. To allow for withdrawals, 400 participants per group were to be included, as also deemed sufficient for the primary objectives.