An Oxford Professor says policy on them has been unclear and inconsistent in some countries.
An Oxford University study has revealed just 25% of people in the UK wore a face mask in late April, compared with almost 85% in Italy.
Professor Melinda Mills says it isn't the public's fault for not using them though, adding that policies and public messaging has differed across the country - and needs to be more consistent.
Her study found that even homemade masks made with the correct material, are effective in reducing the spread of COVID-19, for both the wearer and the people around them.
Oxford's Leverhulme Centre for Demographic Science carried out the study, with the report published today.
Professor Melinda Mills 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 new 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 added, 'We lacked a comprehensive systematic literature review that went beyond medical research. There has been a blind spot in thinking about the behavioural 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.'
Professor Mills also said the public was '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.
She said: "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."
The study also found that loosely woven fabrics, such as scarves, are the least effective in preventing the spread of the coronavirus.
Masks made from high quality material such as high-grade cotton, multiple layers and particularly hybrid constructions are effective.
The report reveals that wearing a cotton mask protects the mask wearer as well as people nearby.
It also highlights five key behavioural factors underpinning the public's compliance to wearing a mask.
- First, they need to understand virus transmission and how masks protect them and others.
- 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'.'
- Socio-political systems, public trust in governments and experts and previous experience with pandemics is also key. The report shows, for instance, how political polarisation can impede a government's ability to provide a coordinated response.
- 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.'
- 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.
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.