The large group of international researchers reviewed dozens of rigorously correct, randomized clinical trials of "physical interventions" against respiratory diseases. These diseases included influenza and COVID-19 during the pandemic, and these researchers failed to find even a “modest effect” on infection or illness rates from any type of mask.
The pooled results of RCTs did not show a clear reduction in respiratory viral infection with the use of medical/surgical masks. There were no clear differences between the use of medical/surgical masks compared with N95/P2 respirators in healthcare workers when used in routine care to reduce respiratory viral infection. Hand hygiene is likely to modestly reduce the burden of respiratory illness, and although this effect was also present when ILI and laboratory‐confirmed influenza were analysed separately, it was not found to be a significant difference for the latter two outcomes. Harms associated with physical interventions were under‐investigated.
