Face mask use by healthy people in the community: Summary of Evidence.

21st August 2020

Face masks aim to reduce the spread of infection by acting as a source control to stop the spread of infection by the person wearing the mask (including those who do not know they are infected) or to protect the wearer from droplet splashes or inhaling airborne contaminants including small (aerosol) and large particle droplets. Mask grades include respirators (classified as PPE designed to also protect against aerosols), medical face masks and non-medical facemasks.

Key points:

• Since the start of the current COVID-19 pandemic, the use of face masks by persons going out in public has been recommended by an increasing number of countries. In Ireland, cloth face coverings are recommended in situations where physical distancing may not be possible and are mandatory on public transport and in shops and other retail outlets.
• Nineteen studies that provide direct evidence on the effectiveness of face mask use in community settings to reduce transmission of respiratory viruses were identified.
• Four studies were conducted in the context of the COVID-19 pandemic, the remaining studies considered influenza, influenza-like illness (ILI), or SARSCoV-1. Eight studies examined the effectiveness of medical masks, nine studies did not specify the type of mask used, one study included both medical and non-medical masks and one study included all types of masks.
• Four observational studies conducted during the COVID-19 pandemic, suggest that face masks may reduce the risk of SARS-CoV-2 infection. Two observational studies that examined the effectiveness of wearing face masks when going out in public suggested that face masks may have been protective against SARS-CoV-1 infection.
• Six randomised control trials (RCTs) set in households provide some weak evidence that medical masks worn by both index cases and healthy household contacts can reduce the risk of secondary household infections, when implemented early and combined with intensified hand hygiene.
• There was no evidence from the included studies that face masks increase harm or introduce a false sense of security leading wearers to neglect hand hygiene.
• The quality of evidence from the studies included was low; two of the studies conducted during the COVID-19 pandemic have not yet been formally peer reviewed.
• There is limited, low certainty evidence based on four observational studies conducted during the COVID-19 pandemic that face masks may reduce the risk of transmission of SARS-CoV-2. Studies from previous pandemic settings and for other respiratory viruses also provide low certainty evidence that the wearing of face masks in community settings reduces the risk of transmission of respiratory pathogens. However, their applicability to COVID-19 is uncertain given possible differences between viruses in their pathogenicity and infectivity and the potential differences in the relative contribution of the different modes of transmission (droplet, aerosol, contact).
• National and international public health guidance is based on low certainty direct evidence of clinical effectiveness and indirect evidence that supports the plausibility of effectiveness of face masks. In addition, SARS-CoV-2 appears to be more infectious than many other respiratory pathogens studied to date based on its basic reproduction number, highlighting the necessity of considering a range of infection prevention control measures, including face masks, to reduce the spread of infection.
• There is an urgent need for more research, particularly high-quality studies that provide direct evidence on the use of face masks by healthy people in the community.

Read the full report: Evidence summary for face mask use by healthy people in the community (hiqa.ie)