2.3 The Scientific Debate on the use of Face masks

• 2.3 The Scientific Debate on the Use of Facemasks

  
  

  By Judith Glynn 

  Professor of Infectious Disease Epidemiology, LSHTM.

  
  

  When you look at pictures from around the world, many people are wearing face masks. And shortages of face masks for health workers and care workers are constantly in the news. So who should be wearing face masks, and why?

  There are different sorts of face mask. Health workers in close contact with infected patients, particularly those performing medical procedures where the virus is likely to get into the air, need maximum protection, with close-fitting masks with respirators (such as N95 or FFP masks). These filter out 95% of particles in the air.

  
  

  Figure 1. N95 mask.
  
  

  But the type of masks we usually see are “surgical” masks: simple disposable masks fitted with ties or elastic. These are designed to reduce the risk of transmission of infection from the wearer, by limiting the spread of droplets (e.g. saliva, coughs, sneezes). They may also provide some protection to the wearer against droplets and splashes, but they are loose fitting and the material does not prevent very small particles in the air (which may contain virus) from passing through.  Nevertheless, they are recommended for those caring for infected patients when respirators are not available and/or for lower risk procedures, as well as for those with symptoms.

  
  

  Figure 2. Disposable surgical mask.
  
  

  The third type is cloth masks, often home-made. They are loose fitting and the weave lets small particles through. Like surgical masks they should prevent some of the spread from coughs and sneezes from the wearer. They probably provide little if any protection to the wearer.

  
  

  Figure 3. Cloth Masks.
  
  

  Some countries have encouraged or enforced widespread use of face masks, as part of physical distancing measures. Others have not. The arguments that have been used are set out below.

  
  

  Arguments against widespread use by the general public

  • There are no trials or other strong evidence of effectiveness in reducing transmission in the population setting
  • They provide very limited protection to the wearer
  • They give a false sense of security: people might feel safe so ignore physical distancing
  • It is important to keep supplies for health workers
  • They may increase risk if incorrectly worn – e.g. people touch their faces more, to adjust the mask, or they may be touched on removal, contaminating fingers
  • They may increase risk if worn too long/re-used – virus can persist on masks
  • Re-usable cloth masks may not be washed properly which might increase risk

  
  

  Arguments for use by the general public

  • Lack of evidence doesn’t mean that they don’t work, and as a physical barrier they should reduce some droplet spread
  • Widespread use in situations where transmission is likely (e.g. public transport, shops, shared work-places) could help reduce transmission
  • Because people can transmit SARS-CoV-2 without having any symptoms it is important that everyone wears masks to prevent transmission.
  • Using cloth masks would still leave the disposable masks for health workers
  • Public education can ensure proper use and frequent washing.
  • Public education can ensure people understand that they are protecting others, not themselves.

  You may be able to think of other arguments for or against.

  What would you recommend if you were responsible for policy?

  
  

  Policy in the UK

  The UK government has suggested that people should wear some sort of face covering when in enclosed spaces indoors, where social distancing may not be possible e.g. on public transport or in shops. Their guidance concedes that wearing a face covering will not protect the wearer, but may avoid transmission of the virus by asymptomatic people. Government advice states that any ‘face covering’ they mean a cloth mask (i.e. not a surgical mask or an N95 mask). The public should not compete with the NHS for access to medical-grade masks.

  
  

  How do you wear a mask safely?

  If you decide you would like to wear a mask, make sure you follow the guidance in the image below. Try to make sure your mask covers your mouth and nose- don’t take it off to talk to people, or to speak on the phone.

  Make sure there are no gaps around the edges of your mask, and avoid touching it whilst wearing it. Face coverings should not be worn by children under 2 years old, or by people with respiratory conditions.

  Bear in mind that even though you’re wearing a mask, you should still practice social distancing, regular hand washing, and self isolation if you develop symptoms.  

  There is guidance on making your own mask here: https://www.gov.uk/government/publications/how-to-wear-and-make-a-cloth-face-covering/how-to-wear-and-make-a-cloth-face-covering

  
  

  Figure 4. Step-by-step guide for using your mask.
  
  

  
  

  Further reading

  Respiratory virus shedding in exhaled breath and efficacy of face masks https://www.nature.com/articles/s41591-020-0843-2

  WHO advice on face masks https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public/when-and-how-to-use-masks

  Face masks for the public during the covid-19 crisis https://www.bmj.com/content/369/bmj.m1435

  Wearing face masks in the community during the COVID-19 pandemic: altruism and solidarity https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30918-1/fulltext

  Image Acknowledgements 

  Figure 1: CDC Public Health Image Library. https://phil.cdc.gov

  Figure 2: Credit: Anna Shvets

  Figure 3: Credit: Julia M Cameron

  Figure 4: World Health Organisation