If the control group still is positive for corona after 7 days in 90% of cases and we anticipate the intervention to get that number to 50%, with an alpha of 0.

If the control group still is positive for corona after 7 days in 90% of cases and we anticipate the intervention to get that number to 50%, with an alpha of 0.05 and a size of 24 in the intervention group, the study has a power of 0.957 and answers the question whether chloroquine stops viral shedding by day 7. This isn't cardiology where we need 50000 patients to find the significance.