[2rF7OoC47]

From the study abstract:

"Our search identified 172 observational studies across 16 countries and six continents, with no randomised controlled trials"

Don't have a chance to read the full article until later. Does anyone know if they are controlling for confounding factors (e.g. urban/rural, public/private settings)?

[irq11]

They are not. They freely mix studies from different circumstances.

For example, the “mask” section mixes data for respirators and surgical masks, and does not differentiate between hospital or community use, source control or PPE, when they make their top-line conclusions.

If you look at the breakouts, you’ll note that most of the data showing effectiveness for masks is for respirator use in hospitals.

[2rF7OoC47]

Surely that's mentioned in the limitations of the study? In my quick scan of the abstract, I don't recall seeing anything about it. Could have missed it though.

[irq11]

It is not in the abstract.