Because those efficacy numbers are complete bs. They're saying that 90% of people in trial didnt get virus after. 50% got placebo, most likely never came in contact or already had it without knowing. So... 10% of 50% not counting those who were dropped from the trial due adverse reactions (a large # if rumors are true) didnt get the cov after. That's basically between a 2 and 3% sample size from total subjects.