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Wearing face masks in the community

Hopefully we’ve made our own views on this topic clear by now, but what does the science say about the pros and cons of “the average person in the street” wearing a mask in public? Here’s an extract from a new paper in The Lancet entitled “Wearing face masks in the community during the COVID-19 pandemic: altruism and solidarity“:

The WHO ha[s] not yet recommended mass use of masks for healthy individuals in the community (mass masking) as a way to prevent infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in its interim guidance of April 6, Public Health England (PHE) has made a similar recommendation.

By contrast, the US Centers for Disease Control and Prevention (CDC) now advises the wearing of cloth masks in public and many countries, such as Canada, South Korea, and the Czech Republic, require or advise their citizens to wear masks in public places.

An evidence review and analysis have supported mass masking in this pandemic. There are suggestions that WHO and PHE are revisiting the question.

People often wear masks to protect themselves, but we suggest a stronger public health rationale is source control to protect others from respiratory droplets. This approach is important because of possible asymptomatic transmissions of SARS-CoV-2.

Authorities such as WHO and PHE have hitherto not recommended mass masking because they suggest there is no evidence that this approach prevents infection with respiratory viruses including SARS-CoV-2. Previous research on the use of masks in non-health-care settings had predominantly focused on the protection of the wearers and was related to influenza or influenza-like illness. These studies were not designed to evaluate mass masking in whole communities.

The authors go on to address that failing of previous studies:

Absence of evidence of effectiveness from clinical trials on mass masking should not be equated with evidence of ineffectiveness. There are mechanistic reasons for covering the mouth to reduce respiratory droplet transmission and, indeed, cough etiquette is based on these considerations and not on evidence from clinical trials. Evidence on non-pharmaceutical public health measures including use of masks to mitigate the risk and impact of pandemic influenza was reviewed by a workshop convened by WHO in 2019; the workshop concluded that although there was no evidence from trials of effectiveness in reducing transmission, “there is mechanistic plausibility for the potential effectiveness of this measure”, and it recommended that in a severe influenza pandemic use of masks in public should be considered. Dismissing a low-cost intervention such as mass masking as ineffective because there is no evidence of effectiveness in clinical trials is in our view potentially harmful.

Mass masking is underpinned by basic public health principles that might not have been adequately appreciated by authorities or the public. First, controlling harms at source (masking) is at least as important as mitigation (handwashing). The population benefits of mass masking can also be conceptualised as a so-called prevention paradox—ie, interventions that bring moderate benefits to individuals but have large population benefits. Seatbelt wearing is one such example. Additionally, use of masks in the community will only bring meaningful reduction of the effective reproduction number if masks are worn by most people—akin to herd immunity after vaccination. Finally, masking can be compared to safe driving: other road users and pedestrians benefit from safe driving and if all drive carefully, the risk of road traffic crashes is reduced.

So there you have it. Mask up if you’re out and about in public. You know it makes sense!