evidence: Last year I wrote that a day may come, when we have evidence about masks that’s so strong, so convincing, only the most extremely biased will still be arguing about it. It is, still, not this day. But digging into a major, wide-ranging new review by Trish Greenhalgh and colleagues clarified several issues for me, and left me optimistic that we will get there. There already is a stronger scientific consensus about the effectiveness of masks than you might think. It’s hard to see, though, because the amount of literature is overwhelming, and the field is clouded by smoke created by a few bombs. [...] Then a couple of trials landed that fuelled enormous debate – the first of them blew past all other scientific articles to take the top spot in Altmetric’s list of the most discussed in 2021. In addition, there were controversial updates of the Cochrane systematic review by Tom Jefferson and colleagues. Based solely on the results of randomized trials, that review has been widely misrepresented as proving that masks don’t work – including by its lead author. It was weaponized by critics of masks and pandemic interventions generally, while taking a beating from people defending mask effectiveness – in The New York Times and Scientific American, for example.