The WHO reported their views on masks in 2019, using data from randomised controlled trials (RCTs) – the gold standard.
‘Ten RCTs were included in the meta-analysis, and there was no evidence that facemasks are effective in reducing transmission of laboratory-confirmed influenza.’
Since then, there has only been one RCT done on COVID19 transmission, in Denmark. It did not find any significant benefit from masks in reducing spread.
The WHO reported their views on masks in 2019, using data from randomised controlled trials (RCTs) – the gold standard.
‘Ten RCTs were included in the meta-analysis, and there was no evidence that facemasks are effective in reducing transmission of laboratory-confirmed influenza.’
https://apps.who.int/iris/bitstream/handle/10665/329438/9789241516839-eng.pdf?ua=1
Since then, there has only been one RCT done on COVID19 transmission, in Denmark. It did not find any significant benefit from masks in reducing spread.
https://pubmed.ncbi.nlm.nih.gov/33205991/