A 2019 World Health Organization review of pandemic mitigation measures, for instance, found "no evidence" that face coverings helped to stop the spread of influenza.
Whether or not studies on influenza transmission can apply to COVID-19 is unknown; the disease's relatively recent emergence means that scientific studies on it are in short supply. Studies can take many month to secure funding, develop methodologies, carry out experiments, interpret the findings, write a research paper and get it peer-reviewed and published.
To bridge that gap, a team of Danish scientists earlier this year sought to carry out a major randomized controlled trial study to determine how effective masks might be at stopping COVID transmission. The study, begun in April, involved around 6,000 Danish citizens, half of whom wore face coverings during "normal behavior" and the other half of whom went without them.
The study concluded in June. Yet the Copenhagen newspaper Berlingske reported this week that it has been rejected by at least three elite medical journals so far — the Lancet, the New England Journal of Medicine, and JAMA, the Journal of the American Medical Association.
"They all said no," Christian Torp-Pederson, one of the study's researchers, told the Danish newspaper this week. He added that the study's scientists "cannot start discussing what [the journals] are dissatisfied with, because in that case we must also explain what the study showed, and we do not want to discuss that until it is published."
