Efficacy
The median follow-up time for cohort 1 was 100 days (IQR, 96-106 days), and for cohort 2, 142 days (IQR, 137-148 days). In cohort 1, 461 (3.2%) symptomatic cases in the vaccine group and 221 (6.1%) in the placebo group were observed, which yielded a vaccine efficacy (VE) of 49.7% (95% CI, 40.8%-57.3%). In cohort 2, 75 (1.6%) symptomatic cases occurred in the vaccine group and 51 (4.3%) in the placebo group, corresponding to a VE of 64.9% (95% CI, 49.7%-59.5%) (