- There is some evidence that face masks and coverings worn by the general public may reduce transmission of the virus in some specific circumstances, particularly in poorly ventilated and crowded indoor spaces.
- Face coverings offer some protection by limiting transmission of virus from the wearer. The degree of protection is uncertain.
- Policy on using face coverings differs across the UK. They are recommended across the UK in circumstances where social distancing is difficult.
- In Northern Ireland face coverings are mandatory on public transport.
- In Scotland face coverings must be used on public transport and in shops.
- In England they are mandatory on public transport and in NHS hospitals and are recommended as one of the additional precautionary measures that should be taken in circumstances when the 2 m gap for physical distancing cannot be maintained. From 24 July face coverings are mandatory in shops, supermarkets, cafes where customers are buying food or drink to take away, banks, building societies, post offices and transport hubs.
- In Wales face coverings are mandatory on public transport and in taxis from 27 July.
- Data from the Office for National Statistics indicates that several occupational groups, including shop workers, are at increased risk of dying from COVID-19. Occupational risk is one factor highlighted by the Government in its evolving policy on mandating face coverings in England. Face masks and coverings are not a substitute for social distancing, hand hygiene and good respiratory etiquette, which remain the most effective ways to limit the transmission of SARS-CoV-2.
- Research demonstrates that clear, consistent and effective public messaging is likely to increase public adherence of wearing face masks and coverings.
- This article was originally published on 3 July and has been updated on 24 July to include the following sections: Occupational, workplaces and risk, and Public attitudes and adherence to wearing face masks and coverings. The timeline has been updated to 27 July.
- This is part of our rapid response content on COVID-19. The article will be updated as the research progresses. You can view all our reporting on this topic under COVID-19.
Face masks and other face coverings (such as home-made cloth masks or scarves) are now widely recommended as one public health measure to limit the transmission of COVID-19. POST’s previous briefing on face masks and coverings explains the different types of masks and coverings, the settings in which they are used, research approaches to test if they reduce the transmission of infection, cultural attitudes to wearing face masks and coverings, and the evolving policy and scientific debate about their use early in the pandemic.
This briefing gives an update on the latest research, the role for face masks and coverings as a mitigating measure in the easing of restrictions on daily life across the UK, public attitudes and practices and a timeline of recent policy developments.
Preventing transmission of COVID-19
SARS-CoV-2 is a new virus that the international research community is responding to with numerous studies on its characteristics, including how it is transmitted between people, both directly or indirectly. This means that the research evidence is changing on a daily basis. Understanding transmission is critical in developing mitigation measures to prevent it. The Scientific Advisory Group for Emergencies (SAGE) provides advice for the UK Government (Scotland has its own expert group providing additional analysis – the Scottish Government COVID-19 Advisory Group), and has a specialist sub-committee, the Environment Working Group, which looks at the environmental aspects of COVID-19. This group published a report summarising the research on transmission and measures to mitigate it on 4 June.
There are three transmission routes for SARS-CoV-2:
- droplet transmission where respiratory droplets are produced when someone coughs or sneezes. If someone is in close contact then they are at risk of being exposed to droplets through the mouth, nose and eyes.
- contact transmission with the virus on contaminated surfaces. Transmission can occur if someone then touches their mouth, nose or eyes.
- aerosol transmission comprising small viral particles that may persist for up to 1 hour.
The first two are the key routes, with good evidence that transmission of the virus is likely to result from close prolonged contact between people through the direct transfer of droplets and indirectly, through touching contaminated objects and surfaces. The evidence for aerosol transmission is weak but is likely to be more of a risk in poorly ventilated and crowded indoor environments.
Transmission also depends on the duration of exposure to the virus, with risk increasing with time of exposure. It is also related to the physical distance to the source; therefore maintaining a 2 m distance is safer than a 1 m distance. There is significant uncertainty about the increased risk associated with being closer to the source; the best estimate on the data available is that risk increases 2–10 fold at 1 m compared with 2 m. Orientation to the source is also relevant: face-to-face contact is riskier than being side-by-side. The uncertainty is also compounded by the fact that is not yet clear how much virus causes an infection in a person. The SAGE Environment Working Group report on transmission summarises the main risks:
- prolonged face-to-face contact with someone at a distance of less than 2 m – risk increases with duration and proximity
- contact transmission increases with proximity to an infected person, number of surfaces touched and frequency of touching the face, and is dependent on viral survival on different surfaces
- risk of aerosol transmission is highest in poorly ventilated spaces
The way the virus disperses is complex and results from numerous interacting outdoor and indoor environmental factors including temperature, humidity and exposure to sunlight, ventilation, building layouts and fixtures.
Consequently, the scientific advice has consistently been that the most effective actions that limit transmission of the virus are thorough hand washing, good respiratory hygiene and social distancing. Social distancing refers to a range of measures, such as maintaining a 2 m gap where possible, avoiding face-to-face contact, limiting the duration of contacts and minimising contact between social groups.
Advice on modifying these measures has been developed in order to facilitate an easing of restrictions on daily life. Face masks and coverings are one measure that have been adopted at different times by the UK governments, either mandated or advisory, according to the context. A timeline of relevant policy announcements is detailed at the end of this article.
The role that face masks and coverings play in limiting community transmission of SARS-CoV-2 is of policy interest because people can be infected with the virus but have no COVID-19 symptoms (asymptomatic) or be infected but have not yet developed symptoms (pre-symptomatic). There is evidence suggesting that a person is most infectious before they become symptomatic. The question is whether transmission of the virus can be reduced if people in these categories cover their nose and mouth and, if so, what degree of protection this offers. This is not straightforward since it depends on the type of face mask used, and the hygiene etiquette practised by those using them.
Respirators and surgical face masks used as part of Personal Protective Equipment (PPE) in health and care settings must meet designated quality standards that differ significantly from face masks that can be manufactured to lower quality standards, and home-made face coverings. These differences include filtration properties, fluid repellence, durability and fit. However, face masks or coverings do not offer any eye protection. Face visors, face shields and goggles are also part of medical PPE, as viruses, including SARS-CoV-2 can be transmitted through the eyes.
The scientific advice has consistently been that face masks and coverings are to be viewed as only one part of an approach that combines multiple public health measures to limit transmission.
Research on masks
Face masks and coverings can offer protection against viral transmission in two ways:
- source control by minimising the dispersal of respiratory droplets from an infected person
- protective effect where the wearer is protected from exposure to droplets produced by others
Respirators are very effective in protecting the wearer from exposure to droplets and aerosols. Surgical face masks give the wearer some limited protection from exposure to droplets but not aerosols; they also block some emission of respiratory droplets produced by the wearer. Their effectiveness is determined by the material, how well they fit and if they are used appropriately. They are used in hospitals and care settings and staff receive training on how to use them. There is some evidence that non-surgical masks and other face coverings offer source control, that is they offer some protection to those around the wearer by blocking some of the droplets they produce and how far they travel, but the extent of protection depends on the material used, the fit, and wearer’s behaviour. Face shields and visors offer some protection against droplet exposure but offer very limited protection against aerosol exposure. There is no evidence that they are effective as a source control. As with face masks and coverings, if they are not used appropriately – for example in the way they are put on and taken off – they can be a source of contamination. The World Health Organization has published guidance on the construction of home-made fabric masks. They recommend that a face covering should have three layers and specifies which textiles should be used in each layer to offer the highest level of protection.
There is no published research from randomised controlled trials on the role of masks or face coverings worn by the general population in the transmission of SARS-CoV-2. One systematic review searched for any studies of the impact of healthy people wearing masks to prevent COVID-19 transmission. It did not find any such studies. One clinical trial is in progress to examine if face masks and coverings in community settings contribute to reduced disease transmission of COVID-19:
- A clinical trial in Denmark of 6,000 people will compare wearing face masks with not wearing face masks. All participants will be instructed to follow national public health guidance. If they develop symptoms they will be tested during the study. They will all be screened at the end of the study to see if they have produced antibodies against COVID-19.
The approaches used to test whether masks reduce viral transmission and the complexities of this type of research are discussed in POST’s previous article on face masks. There is some research on the role of masks in limiting community transmission of other respiratory viruses, such as influenza virus, but the evidence to support their use is weak. There is some weak evidence of an effect if a mask is worn by an infected person, but making accurate estimates of the degree of protection offered by face masks based on the available evidence is not possible at the moment. A review of multiple studies published in The Lancet concluded that there is role for masks and eye protection in reducing exposure to COVID-19, but notes that the certainty about the evidence is low. Most studies in this review were about other coronaviruses and none of the COVID-19 studies included were conducted in community settings. Many other studies report that compliance with wearing masks varies, and this also has an impact on how effective they are.
There is consensus that the use of face masks, coverings and eye protection by the general public may offer some limited protection in some contexts, but are not a substitute for practising other behaviours that have a significant impact on transmission and for which the evidence is strong: frequent hand washing, respiratory hygiene, physical distancing and limiting social contact. Some stakeholders have argued for a precautionary approach to be taken to the use of face coverings because large-scale trials will be difficult to conduct and will take time to complete.
Occupation, workplaces and risk
POST’s first article on face masks and coverings outlined the scientific evidence about their role in preventing viral transmission. There is very strong evidence for their use as a preventive measure in health and care settings. There is some limited evidence on their effectiveness when used in the community. There is increasing knowledge about the disparities in health outcomes for different people if they have COVID-19 and the approaches that might be taken to mitigate the risks. Risks associated with workplaces and occupation are of concern. Higher risks of contracting and spreading the virus are associated with making numerous social contacts of long duration and in close proximity. Analysis by the Office for National Statistics (ONS) in April indicated that low paid professions that involve close contact with lots of different people are linked to an increased risk of death from COVID-19.
On 13 July the Welsh Government announced that face coverings will be mandatory on public transport and in taxis. The latest policy announcements by the UK and Scottish Governments mandate the use of face coverings in shops and other enclosed spaces. In his statement, the Health and Social Care Secretary highlighted that sales and retail assistants, cashiers and security guards are at increased risk from COVID-19 than the general population. Data from analysis by the ONS suggest that a range of other occupations are at increased risk; there is no policy to mandate face coverings in these occupational settings.
The ONS publishes data on COVID-19 related deaths by occupational groups for men and women aged 20 to 64 years old in England and Wales. It is not possible to say conclusively that differences in death rates between occupations result from exposure to COVID-19 at work. Other factors that may play a role are ethnicity, place of residence, health status, level of deprivation, and the occupation of other household members. Two-thirds of deaths involving COVID-19 in the working-age population (those aged 20–64 years) were in men. In men, the occupations with the highest rates of COVID-19 related death were:
- Factory workers: 73.3 deaths per 100,000 men.
- Security: 68.2 deaths per 100,000 men.
- Taxi and cab drivers and chauffeurs : 65.3 deaths per 100,000 men.
- Chefs: 56.8 deaths per 100,000 men.
- Care workers: 50.1 deaths per 100,000 men.
- Bus and coach drivers: 44.2 deaths per 100,000 men.
- Construction workers: 42.1 deaths per 100,000 men.
- Sales and retail assistants: 34.2 deaths per 100,000 men.
- Service occupations (bar staff, leisure and theme park attendants): reliable rates for this group could not be calculated.
- Care workers: 25.9 deaths per 100,000 women.
- National government administrative jobs: 23.4 deaths per 100,000 women.
- Sales and retail assistants: 15.7 deaths per 100,000 women.
The Health and Safety Executive has published guidance on how risks can be mitigated in workplaces, to ensure that they are COVID-secure, including the use of PPE for employees in non-healthcare settings. A report for SAGE on reducing transmission in occupations that involve multiple contacts recommends wearing a face covering if 2 m social distancing is not possible.
There is ongoing debate about the development and inconsistencies in policy on the use of face coverings in the community. For example, there is no requirement for staff in retail settings or other service occupations to wear face coverings. Face coverings are not mandated in settings where other occupational groups are at higher risk than shop workers and where durations of exposure may be longer. Their use in some settings, such as pubs and bars, where long duration exposures are likely, is complicated by the frequency with which they would need to be removed to drink and eat, which limits their usefulness. This has led to commentary on mixed and confusing messages to the public, discussed in the next section. The day before face coverings become mandatory in shops and supermarkets in England, the UK Government issued a press release outlining that they must also be worn in shopping centres, in cafes if a customer is buying food to take away, in banks, building societies, post offices and in transport hubs.
Public attitudes and adherence to wearing face masks and coverings
According to the COVID-19 Behaviour Tracker, a global representative survey run by the Institute of Global Health Innovation at Imperial College London with YouGov, as of 12 July, 38% of people in the UK reported wearing a face mask when in public places. This is a steady increase over time from a reported level of 2% on 20 March, just before lockdown measures were implemented. Lower levels of usage were reported in Australia (20%), Finland (7%), Sweden (6%), Norway (5%) and Denmark (4%). By contrast, the highest levels of usage were reported in Singapore (90%), Spain (88%), Malaysia (86%), Indonesia (85%), the Philippines (84%), Thailand (83%), Italy (83%), Taiwan (81%) and the United Arab Emirates (81%).
A rapid evidence review by the Royal Society and British Academy looked at social and behavioural factors related to public adherence to wearing face masks and coverings. It found high-quality evidence with consistent results for several factors:
- Personal and cultural beliefs and understanding of how respiratory viruses are spread. This includes people’s perceptions of how the virus is spread and whether it can be spread by asymptomatic individuals; whether they consider face coverings are used for individual protection against contracting the virus versus wearing one to protect others; whether people feel able to self-diagnose based on their symptoms and to use this to inform their behaviours; and people’s beliefs about the effectiveness of face coverings in reducing the health threat and perceived barriers of face coverings.
- Perceived likelihood of infection and perceived benefits. Individual risk perceptions about contracting and transmitting the virus shape the use of face masks and coverings. People often view themselves as less vulnerable than ‘others’ and underestimate their own risk. For example, people may state their difference to other groups or environments that are perceived to present a higher risk, such as groups who need to be shielded, or other geographical areas.
- Previous national experience with pandemics and culture of mask wearing. Countries with previous experience with viral infections such as SARS and MERS coronaviruses have had more widespread and earlier use of face masks and coverings during COVID-19. In nations where individuals have previously worn face masks for other reasons, such as pollution (for example India and China), there is also higher use. There is moderate evidence that socio-political systems, such as how socially cohesive a society is, and levels of trust in government are also important.
- Individual characteristics. Wearing face masks or coverings can be influenced by several individual characteristics, including whether a person belongs to a group considered more likely to die if infected, socio-demographic characteristics including age and sex, as well as personality and physical traits, such as their activity level and whether they wear glasses.
- Perceived barriers around access and comfort. Research shows that unless people feel strongly able to control a threat, fear is likely to lead to a defensive and negative response. Surveys suggest that a shortage of face masks and protective equipment for medical staff produced a feeling amongst the public that face masks were unavailable or that wearing face masks would unduly compete with medical resources. Resource constraints, such as lack of money to buy or inability to make a face covering, may also compound feelings of helplessness. Some evidence suggests that appropriate fit is important to avoid adjusting or removing the mask and that this can be affected by face shape and wearing of glasses. People also have concerns about environmental waste in relation to disposable masks.
Data indicate that countries without a history of wearing face masks and coverings amongst the general public have rapidly adopted their use during the COVID-19 pandemic. For example, a representative survey measuring health behaviour by the Max Planck Institute for Demographic Research looked at attitudes and behaviours surrounding COVID-19 across eight countries (Belgium, France, Germany, Italy, the Netherlands, Spain, UK and the US) between 13 March and 19 April. In a pre-print article that has not yet been reviewed, the authors report substantial increases over the time period for six of the eight countries studied (not in Belgium and the Netherlands), with sharp increases in Italy, Spain and the US.
The COVID-19 Behaviour Tracker found that, as of 15 July, the majority of people in the UK reported that they were very or quite willing to wear a face mask if either it were law (86%), government advised it (76%), international organisations advised it (71%) or if most people did it (66%). When wearing a mask, people reported feeling very much or somewhat better protected (79%), that they were setting a good example to others (74%) and proud of their contribution towards stopping the spread (68%). However, they also reported feeling that it was hard to communicate (65%) and uncomfortable (60%) when wearing a mask.
The rapid evidence review by the Royal Society and British Academy also looked at the relationship between public adherence to face mask and coverings and other non-pharmaceutical interventions. Using data from the Max Planck Institute survey they found that in all of the eight countries, people were most likely to practice social distancing and handwashing, and to avoid public transport. Use of hand sanitiser and face coverings varied between countries.
The Royal Society and British Academy conclude that face masks and coverings should be seen as part of a ‘policy package’, and reviewed alongside other measures including hand hygiene, sanitisers and social distancing. They also state that clear, consistent, transparent and effective public messaging is vital to public adherence of wearing face masks and coverings, and that conflicting policy advice and information without a clear source raises scepticism, generates confusion and reduces adherence.
Scientific advice and policy timeline on community use of face masks and coverings in the UK
Scientific advice and policy developments on the use of face masks and coverings are outlined in this timeline:
6 April: WHO release interim guidance
WHO interim guidance advises that there is insufficient evidence to support the use of face masks and covering by the general public as a way to reduce disease transmission.
Available evidence prior to 6 April
4 February: New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG – a Government advisory committee) reports to SAGE that there is limited evidence to support the public wearing face masks as a preventative measure but some evidence that if symptomatic individuals wear surgical face masks this may reduce transmission to other people.
28 April: Face coverings recommended in Scotland
Scotland: recommends face coverings in enclosed spaces where social distancing is difficult, as a precautionary measure.
Available evidence prior to 28 April
7 April: NERVTAG concludes that increased use of masks would have minimal effect in preventing the wider population from infection.
9 April: SAGE considers a rapid evidence review about community use of face masks prepared by the Usher Network for COVid Evidence Reviews (UNCOVER) on 7 April.
13 April: NERVTAG report on face mask use in the community and options for their use.
14 April: SAGE considers an evidence review covering dispersion of the virus and potential steps to mitigate them in different environments, with some weak evidence that face masks worn by infected people may offer a very small protective effect.
16 April: SAGE view that masks should be prioritised for high-risk environments, recognises a marginal benefit in other settings but that this should only be considered as part of reducing social distancing measures later on.
20 April: The Scientific Pandemic Influenza Group on Behaviours (SPI-B) reports to SAGE on behavioural science perspectives on the use of face masks in the community.
21 April: SAGE concludes that evidence for using face cloth coverings in the community for source control and protection is weak, but they could be recommended as a precautionary measure for short durations in high-risk indoor settings where social distancing is not possible, in the context of releasing lockdown measures.
7 to 12 May: Face coverings recommended in Northern Ireland and England
In Northern Ireland on 7 May: Government recommends face coverings in enclosed spaces where social distancing is not possible.
In England on 11 May: Government advises the public to use a face covering in enclosed spaces (shops and public transport) where social distancing is difficult. Public Health England publishes advice on how to make and wear a face covering.
In Wales on 12 May: Chief Medical Officer publishes rationale for not recommending face coverings.
Additional evidence published up to 7 May
7 May: SAGE considers a report on environmental mitigation measures.
5 June: WHO updates advice on face masks
WHO updates advice, stating that national governments can encourage the general public to wear face masks or coverings in specific circumstances (such as when social distancing is difficult) as part of a comprehensive public health approach. Detailed guidance on mask types, settings in which they might be used and communication with the public.
Additional evidence published prior to 5 June
4 June: SAGE endorses the Environment and Modelling Group’s report on transmission and mitigation measures and another on the use of masks to reduce transmission in hospitals. SAGE tasks the Care Homes sub-group to consider the effects of mask wearing in care settings to reduce transmission.
9 June: Wales release new recommendations
Wales recommends face coverings in circumstances where social distancing is not possible.
14 June: Wales Chief Medical Officer releases guidance
Wales: Chief Medical Officer updates advice on when face masks or coverings should be worn; public use is supported but not mandatory.
Additional evidence published prior to 14 June
11 June: SAGE endorses a report on reducing transmission in high connectivity occupations. The report recommends face coverings for people (and people they will encounter) in high contact roles when 2 m social distancing is not possible.
15 June: Face coverings become mandatory in England
England: face coverings are mandatory on public transport. Surgical face masks mandatory for all NHS staff in hospitals, and face coverings for outpatients and visitors.
19 June: UK alert level changes
COVID-19 alert level changes from 4 to 3 across the UK.
22 June: Face coverings become mandatory in Scotland
Scotland: face coverings mandatory on public transport and advises that face coverings are worn in closed environments.
Additional evidence published prior to 22 June
19 June: Report on face masks for the general public carried out by the Data Evaluation and Learning for Viral Epidemics (DELVE) group in the Royal Society is published by SAGE.
23 June: Changes in lockdown measures announced
Prime Minister announces changes to public health measures applicable from 4 July.
4 July: Physical distancing guidance changes
2 metre physical distancing guidance changes: in circumstances where this is not possible a 1 metre distance should be observed, supplemented by other measures to mitigate the increased risk – this includes face masks and coverings.
10 July: Scotland and Northern Ireland increase face covering measures
Scotland: face coverings become mandatory in shops.
Northern Ireland: face coverings become mandatory on public transport.
13 July: Wales increases face covering measures
In Wales, the First Minister announces that face coverings will be mandatory on public transport and in taxis from 27 July.
14 July: England announces increased face covering measures
Health and Social Care Secretary announces that face coverings will become mandatory in shops and supermarkets in England from 24 July.
23 July: England announces increased face covering measures
The Department of Health and Social Care publishes a press release outlining that in England face coverings must be worn in an additional range of enclosed public spaces in addition to shops and supermarkets on 24 July.
24 July: New measures come into effect in England
Face coverings become mandatory in shops and supermarkets, shopping centres, cafes where customers are buying food and drink to take away, banks, building societies, post offices and transport hubs.
27 July: New measures come into effect in Wales
Face coverings become mandatory on public transport and in taxis in Wales.
You can find more content from POST on COVID-19 here.