Good news: masks are a huge help.
A side “how to read this” note: calls for randomized trials is really people falling back on their comfort zone of “that’s how we test medicine” but it is *not* necessary or even possible for many interventions, so requiring randomized double-controlled studies introduces a different kind of bias: it excludes interventions where that isn’t possible, and adds a bias towards medications instead of prevention. This bias drives the costs of healthcare up, in that treatment rather than prevention is almost always more expensive. Other controls are possible, and observing after the fact “natural experiments” and meta-analyses like this also provides huge amounts of information that can be acted upon. In a pandemic, especially, wait and see on known effective preventative measures kills people. When the intervention is low risk and high payoff, just do it, and keep taking data to confirm or disprove whether it works!
That said: read the attached article.