Originally Posted by mopek1

That's a good question but from what I understand it's too hard to tell unless the data was overwhelming.

Masks are one variable in a complex system of variables. You can only say they don't work if they don't correlate with the changes in cases.

For example if everyone suddenly wore masks and the cases spiked then they don't work. It could be because of another variable but in most of the countries and states the variables stayed the same or became even more resolute (lock downs) so nothing changed except for masks.

But you can't say they make it worse as there are other variables to consider. Maybe cases spiked because young people are partying etc...