>A May 2020 meta-study on pandemic influenza published by the US CDC found that face masks had no effect, neither as personal protective equipment nor as a source control.
>A July 2020 review by the Oxford Centre for Evidence-Based Medince found that there is no evidence for the effectiveness of cloth masks against virus infection or transmission.
>A Covid-19 cross-country study by the University of East Anglia found that a mask requirement was of no benefit and could even increase the risk of infection.
>An April 2020 review by two US professors in respiratory and infectious disease from the University of Illinois concluded that face masks have no effect in everyday life, neither as self-protection nor to protect third parties (so-called source control).
>An article in the New England Journal of Medicine from May 2020 came to the conclusion that cloth face masks offer little to no protection in everyday life.
>An April 2020 Cochrane review (preprint) found that face masks didn’t reduce influenza-like illness (ILI) cases, neither in the general population nor in health care workers.
>An April 2020 review by the Norwich School of Medicine (preprint) found that “the evidence is not sufficiently strong to support widespread use of facemasks”, but supports the use of masks by “particularly vulnerable individuals when in transient higher risk situations.”
>A July 2020 study by Japanese researchers found that cloth masks “offer zero protection against coronavirus” due to their large pore size and generally poor fit.
>A 2015 study in the British Medical Journal BMJ Open found that cloth masks were penetrated by 97% of particles and may increase infection risk by retaining moisture or repeated use.
>An August 2020 review by a German professor in virology, epidemiology and hygiene found that there is no evidence for the effectiveness of cloth face masks and that the improper daily use of masks by the public may in fact lead to an increase in infections.
>An analysis by the US CDC found that 85% of people infected with the new coronavirus reported wearing a mask “always” (70.6%) or “often” (14.4%). Compared to the control group of uninfected people, always wearing a mask did not reduce the risk of infection.