RCT is unlikely to be a good tool to determine the effectiveness of masks, if for no other reason, compliance is marginal at best (how do you recognize &record every instance when someone pulls it down for a short time exposing their nose or both airways?).
Perhaps the best evidence that even badly used masks are effective is that measures such a using masks for a year killed every instance of a strain of flu - deas, gone, extinct.
Just by reducing the R0 value to the point where there were no survivors. (but not enough that more virulent COVID-19 strains couldn't survive).
Masks, particularly N95-level, work. Period. Not perfectly, nothing does. But they work. Regardless of any FUD you may want to spread.
Perhaps the best evidence that even badly used masks are effective is that measures such a using masks for a year killed every instance of a strain of flu - deas, gone, extinct.
Just by reducing the R0 value to the point where there were no survivors. (but not enough that more virulent COVID-19 strains couldn't survive).
Masks, particularly N95-level, work. Period. Not perfectly, nothing does. But they work. Regardless of any FUD you may want to spread.