This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection.
As recently as October 2019 WHO guidelines did not recommend masks of any sort for "epidemic and pandemic influenza"
Ten RCTs were included in the meta-analysis, and there was no evidence that face masks are effective in reducing transmission of laboratory-confirmed influenza.
There is a moderate overall quality of evidence that face masks do not have a substantial effect on transmission of influenza.
Reusable cloth face masks are not recommended. Medical face masks are generally not reusable, and an adequate supply would be essential if the use of face masks was recommended. If worn by a symptomatic case, that person might require multiple masks per day for multiple days of illness.
Some Danish researchers did a more recent study that journals are refusing to publish. From that you can probably guess they came to similar conclusions as the 2014 study and 2019 WHO guidelines.
A cluster randomised trial of cloth masks compared with medical masks in healthcare worker is one which showed worse outcomes for healthcare workers wearing cloth masks when compared against the control group of "standard hospital practice" (which included periods of time when medical masks were worn and when they weren't).
As recently as October 2019 WHO guidelines did not recommend masks of any sort for "epidemic and pandemic influenza"
Some Danish researchers did a more recent study that journals are refusing to publish. From that you can probably guess they came to similar conclusions as the 2014 study and 2019 WHO guidelines.