[M T]

For example, this meta analysis suggests that it doesn't help to prevent influenza transmission:

https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza. We similarly found limited evidence on the effectiveness of improved hygiene and environmental cleaning.

I am just naturally cynical against any measure that is advocated as a "magic bullet" (not saying that you are making that assertion).  Experience has shown me that these are few and far between.  Usually, a long slog of small, incremental improvements are needed, rather than a single intervention.

Likewise, I'm just as cynical against studies that find nothing is good enough.  They mix studies together like apples & oranges and say that orange cider isn't very good, even though one did apple cider and the other did orange juice.  I'm sure it will be quoted by those supporting not using masks, not washing hands, not coughing into elbows, or not washing surfaces.  This was out in early release in March at the CDC when I was looking at evidence about face masks back when the CDC was insisting that there was no reason to wear masks unless you're taking care of a sick person.

[M T]

For example, this meta analysis suggests that it doesn't help to prevent influenza transmission:

https://wwwnc.cdc.gov/eid/article/26/5/19-0994_article

Although mechanistic studies support the potential effect of hand hygiene or face masks, evidence from 14 randomized controlled trials of these measures did not support a substantial effect on transmission of laboratory-confirmed influenza. We similarly found limited evidence on the effectiveness of improved hygiene and environmental cleaning.

I am just naturally cynical against any measure that is advocated as a "magic bullet" (not saying that you are making that assertion).  Experience has shown me that these are few and far between.  Usually, a long slog of small, incremental improvements are needed, rather than a single intervention.

Likewise, I'm just as cynical against studies that find nothing is good enough.  They mix studies together like apples & oranges and say that orange cider isn't very good, even though one did apple cider and the other did orange juice.  I'm sure it will be quoted by those supporting not using masks, not washing hands, not coughing into elbows, or not washing surfaces.  This was out in early release in March at the CDC when I was looking at evidence about face masks back when the CDC was insisting that there was no reason to wear masks unless you're taking care of a sick person.