Wear homemade masks when you venture outdoors

The Guardian repeats today what we have been saying for quite some time:

The public should wear homemade masks when they venture outdoors to help reduce the spread of coronavirus, according to scientists who claim Britain’s masks policy does too little to prevent infections.

Prof Sian Griffiths, who led the Hong Kong government’s investigation into the 2003 Sars epidemic, said Britain should adopt the same approach as the US, where people are advised to make their own “cloth face coverings” and wear them in public spaces.

Trish Greenhalgh, a professor of primary care health sciences at Oxford University who recently completed a review on face masks, also advocated the use of masks in public and suggested an old T-shirt combined with kitchen paper would suffice.

The Guardian has some suggestions on how to make your own face mask, as indeed do we. Take a look here.

However some would have you believe that wearing a face mask is not such a great idea. The New Scientist for example. According to Jessica Hamzelou in a possibly paywalled article:

As cases of covid-19 continue to rise, many people are choosing to wear a face mask when out in public – but do they work?

Some have also been using cloth face coverings, but these aren’t up to the job, says Raina MacIntyre at the University of New South Wales in Sydney.

In 2015, MacIntyre and her colleagues ran a clinical trial pitting cloth masks against medical ones. The team provided 1607 healthcare workers at 14 hospitals in Hanoi, Vietnam, with either disposable medical masks or reusable cloth ones, which could be washed at home at the end of the day they were worn. Those that wore cloth masks were significantly more likely to catch a virus, the team found.

It seems that I need to point out to Jessica that just because an academic study finds that DIY masks aren’t as effective as pukka medical masks that doesn’t mean that they are useless. She continues:

But what about the rest of us? In an attempt to answer this question, Paul Hunter at the University of East Anglia, UK, and his colleagues looked at 31 published studies on the efficacy of face masks.

Overall, the evidence suggests there may be a small benefit to wearing some kind of face covering. They do seem to prevent sick people from spreading the virus, but the evidence is weak and inconsistent, says Hunter.

“Our view is that there was some evidence of a degree of protection, but it wasn’t great,” he says. “So we still don’t effectively know if face masks in the community work.”

It seems masks “prevent sick people from spreading the virus”. You can spread the SARS-CoV-2 virus before you show any symptoms, so wear a mask to prevent other people possibly catching your bugs!

Scientists say so, and somewhat grudgingly so does the New Scientist. In the current climate I wouldn’t go out in a public place without one:


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!