Fig. 2

Kaplan–Meier plot of occurrence of RT-PCR-confirmed COVID-19. Shown are the primary endpoint of this trial: cumulative incidence of COVID-19 from exposure(a) and days from exposure to COVID-19 confirmed (b) in the full analysis population (n = 513). COVID-19 patients were defined by RT-PCR tests of oropharyngeal swab or rapid antigen tests. The COVID-19 incidence was analyzed using the Kaplan–Meier method and log-rank test. The time from exposure to confirmed SARS-CoV-2 infection was analyzed using Wilcoxon rank-sum test