Cloth face coverings, masks are effective in reducing the spread of COVID-19, study says

Oxford UniversityJul 9 2020

Cloth face coverings, even homemade masks made with the correct material, are effective in reducing the spread of COVID-19 - for the wearer and those around them - according to a new study published today from Oxford’s Leverhulme Centre for Demographic Science.

The report, investigates the effectiveness of different face mask types and coverings, including an international comparison of policies and behavioral factors underlying usage. It is published jointly today by the British Academy and the Royal Society as part of Royal Society’s SET-C (Science in Emergencies Tasking – COVID-19) group,

Professor Melinda Mills, Director of the Leverhulme Centre and author of the study, Face masks and coverings for the general public: Behavioral knowledge, effectiveness of cloth coverings and public messaging, says, ‘The evidence is clear that people should wear masks to reduce virus transmission and protect themselves, with most countries recommending the public to wear them. Yet clear policy recommendations that the public should broadly wear them has been unclear and inconsistent in some countries such as England.’

The Oxford study shows that, just days after the WHO announced the pandemic in mid-March, many countries (some 70) immediately recommended mask wearing. That number  grew to more than 120 countries. Most require mask wearing everywhere in public. Asian countries with previous experiences of the SARS' outbreak saw early and virtually universal mask usage.

But Professor Mills maintains, ‘We lacked a comprehensive systematic literature review that went beyond medical research. There has been a blind spot in thinking about the behavioral factors of how the general public responds to wearing masks. Also, by looking at lessons learned about face mask wearing from previous epidemics and other countries, we get a broader and clearer picture.’

The study’s key findings are:

• Cloth face coverings are effective in protecting the wearer and those around them.
• Behavioral factors, including how people understand the virus and their perceptions of risk, trust in experts and government, can adversely affect mask wearing.
• Face masks are part of ‘policy packages’ that need to be seen together with other measures such as social distancing and hand hygiene.
• Clear and consistent policies and public messaging are key to the adoption of wearing face masks and coverings by the general public

Professor Mills maintains, ‘The public is confused about wearing face masks and coverings because they have heard the scientific evidence is inconclusive and advice from the WHO and others has changed. People also feared they might be competing with scarce PPE resources and they need clear advice on what to wear, when to wear them and how to wear them.’

Around the world, the study finds, ‘Next to hand washing and social distancing, face masks and coverings are one of the most of widely adopted non-pharmaceutical interventions for reducing the transmission of respiratory infections.’

But, the study shows, some coverings are not as effective as others. Loosely woven fabrics, such as scarves have been shown to be the least effective.

Attention must also be placed on how well it fits on the face; it should loop around the ears or around the back of the neck for better coverage. The general public does not need to wear surgical masks or respirators. We find that masks made from high quality material such as high-grade cotton, multiple layers and particularly hybrid constructions are effective. For instance, combining cotton and silk or flannel provide over 95% filtration, so wearing a mask can protect others."

Professor Melinda Mills, Director of the Leverhulme Centre

Today’s report also finds that wearing a cotton mask protects the mask wearer as well - combining all research on cloth masks in a new meta-analysis.

There is a general assumption that countries such as the UK, which have no culture or history of mask wearing, will not rapidly adopt them. But this just doesn’t hold when we look at the data. As of late April, mask-wearing was up to 84% in Italy, 66% in the US and 64% in Spain, which increased almost immediately after clear policy recommendations and advice was given to the public.’

Professor Melinda Mills

The study concludes, ‘Public communications must be clear, consistent and transparent with inconsistent and premature information raising scepticism and lowering compliance,’ and reports ‘Wearing a face mask in the UK has had a very low uptake (around 25% as of late April 2020)’.

The report finds that a lack of clear recommendations was likely attributed to an ‘over-reliance on an evidence-based approach and assertion that evidence was weak due to few conclusive RCT (randomized control trial) results in community settings, discounting high quality non-RCT evidence.’

Professor Mills insists, ‘RCTs don’t fit well when looking at behavior and it was clear that high quality observational and behavioral research had been largely discarded. It is hard to understand why the policy resistance has been so high. There have been no clinical trials of coughing into your elbow, social distancing and quarantine, yet these measures are seen as effective and have been widely adopted.’

By learning from mask-wearing experiences from previous epidemics, such as SARS, H1N1 and MERS, today’s review revealed five key behavioral factors underpinning the public’s compliance to wearing a mask.

1. First, they need to understand virus transmission and how masks protect them and others.
2. Risk perception was also essential. Professor Mills says, ‘We learned from previous pandemics that individuals underestimate their own risks of contracting the virus or transmitting it to others and think that ‘it won’t happen to me’.’
3. Socio-political systems, public trust in governments and experts and previous experience with pandemics is also key. The report shows, for instance, how political polarization can impede a government’s ability to provide a coordinated response.
4. Individual characteristics were also important with ‘younger people and men having a lower threat perception and compliance of interventions’. Professors Mills notes, ‘Women have a higher incidence of compliance with public health measures such as wearing face coverings, which may a contributing factor the higher COVID-19 deaths amongst men.’
5. Barriers to wearing face masks were also isolated as paramount including lack of supply of surgical masks and perceived competition with medical resources, resource constraints to obtain coverings and concerns about the comfort and fit of wearing them.