The high risk of bias in the trials, variation in outcome measurement, and relatively low adherence with the interventions during the studies hampers drawing firm conclusions.
aka: We can't decide whether masks (or other interventions, including hand washing, etc) worked as all the examples we looked at were a clusterfuck of many people pulling in opposite directions preventing any clear conclusion from being drawn.
Harms associated with physical interventions were under‐investigated.
Sufficient clean data is lacking.
Further:
There is a need for large, well‐designed RCTs addressing the effectiveness of many of these interventions in multiple settings and populations, as well as the impact of adherence on effectiveness, especially in those most at risk
ie. They don't believe the matter is settled by any means.
The most interesting part is the selection criteria.
Looking at the section Characteristics of included studies it appears some effort was made to trawl two decades of global trials in order to find those least likely to have any good conclusion.
Many of the trials look at the effectiveness of low level encouragement to try an intervention at a time and low location with relatively low risks, leading to intermittent uptake and noisy data.
Further:
ie. They don't believe the matter is settled by any means.The most interesting part is the selection criteria.
Looking at the section Characteristics of included studies it appears some effort was made to trawl two decades of global trials in order to find those least likely to have any good conclusion.
Many of the trials look at the effectiveness of low level encouragement to try an intervention at a time and low location with relatively low risks, leading to intermittent uptake and noisy data.