I am long since tired of this debate, and I see that a lot of people are not joining it in the best of faith. I can pass along a few updates, namely this study, with some critical commentary attached. And here is more on the Bangladeshi mask RCT. With more data transparency, it does not seem to be holding up very well.
That said, I am not sure that either calculation really matters. Any good assessment of mask efficacy has to be radically intertemporal in nature, and I mean for the entirety of the pandemic. “Not getting infected” now may well raise your chance of getting infected later on, and that spans for longer than any feasibly designed RCT. And have you heard about the new “Nu” variant? It may turn out not to matter, but it does remind us that the pandemic is not over yet.
As a simple first approximation, think of the real value of masks as “a) how many infections are delayed for how long, plus improvements in treatment in the meantime, plus b) how many infections are avoided altogether.” Even a well-designed RCT is going to focus on a version of b), but only for a limited period of time. The extant studies don’t at all consider “plus improvements in treatment in the meantime,” or when some of those protected by masks for say a year or two might nonetheless later catch Covid later yet. So those RCTs, no matter what their results, are grabbing only one leg of the elephant.
To make matters more complicated yet, a “very small” efficacy for masks might (yes, might) translate into a much larger final effect, due to effective R (sometimes) being greater than 1. So finding a very small effect for masks doesn’t mean masks are only slightly effective. As the pandemic is ending, you might (again might) have had one less “pandemic cycle” than if you hadn’t tried masks at all. You can think of masks as a kind of lottery ticket on “one big gain,” paying off only when the timing is such that the masks have helped you choke off another Covid wave. Again, the RCT is not capable of estimating that probability or the magnitude of its effect.
Yet another part of my mental model of masks has evolved to be the following. You have two sets of countries, countries that manage Covid well and countries that don’t, argue all you want who goes into which bin but that isn’t the point right now.
Now consider the countries that don’t manage Covid well. They might wish to stretch out their epidemics over time, so that better treatments arrive, subject to economic constraints of course. But the countries that manage Covid well probably want the poorly-managed countries to reach herd immunity sooner rather than later, if only to lower the ongoing risk of transmission from a poorly-managed country to a well-managed country. And to lower the risk of those countries birthing new variants, just as southern Africa now seems to have birthed the Nu variant.
So we have two major points of view, represented by multiple countries, one wanting quicker resolution for the poorly managed countries but the other wanting slower resolution. Does any study of masks take those variables into account? No. Nor is it easy to see how it could.
To be clear, I am not arguing masks don’t work, nor am I making any claims about how much masks may or may not protect you individually, or the people you interact with. I am claiming that at the aggregate social level we are quite far from knowing how well masks work.
I say it is third doses we should be doubling down on, not masks. To be clear, I am fine with wearing masks myself, I am used to it, and I dislike it but I don’t hate it. On this issue, I am not one of those people translating his or her own snowflake-ism into some kind of biased policy view.
But the emerging science on third doses is much stronger, and most countries have been dropping the ball on that one.