June 10, 2020

expert reaction to modelling framework study looking at effectiveness of facemasks in combination with lockdown in managing the COVID-19 pandemic

A study, published in Proceedings of the Royal Society A, looked at the effectiveness of facemasks in combination with lockdown in managing the COVID-19 pandemic.

Dr Ellen Brooks Pollock, Senior Lecturer in Veterinary Public Health, University of Bristol, said:

“While face masks might be able to reduce transmission in some settings, such as shops or public transport, it is unlikely that face masks will prevent transmission for close and sustained social contacts, such as at home, because it would be impractical to wear a facemask effectively for 24 hours a day. In this paper, the authors optimistically assume that 100% of transmission events could be prevented with face masks. In reality, 15% of contacts and a third of all contact hours occur in the home, and therefore these transmission events would not be prevented with face mask use. Therefore, the likely impact of face masks is much smaller than is predicted in this modelling study.”

Prof Trish Greenhalgh FMedSci, Professor of Primary Care Health Services, University of Oxford, said:

“This study on face coverings has modelled a number of scenarios – including the possibility that not everyone may comply with the policy, people may not follow strict infection control procedures and the face covering may increase contagion (for example by being discarded and touched by someone else). The findings are encouraging: it appears that face coverings are likely to be an effective population measure even if people make mistakes putting them on and taking them off, and even if some people become infected as a result of touching a discarded face covering. This is because the benefits of face coverings in reducing droplet infection in the population (a large effect) outweigh the potential harms of incorrect use (a small effect). Overall, the model demonstrates that face coverings worn by a large percentage of the population (but not everyone) will be a crucially important measure in preventing a second and third wave of COVID-19 as we come out of lockdown. The findings are reassuring for those of us who sometimes don’t follow perfect ‘donning’ and ‘doffing’ procedures: these are important for doctors and nurses when treating contagious patients, but the rest of us can relax because ‘good enough’ use of face coverings is likely to have the desired effect.”

Prof Keith Neal, Emeritus Professor of the Epidemiology of Infectious Diseases, University of Nottingham, said:

“Clearly there is some face validity to the suggestions that the more people who wear masks the more impact this might have on the spread of COVID-19, but this is highly dependent on the effectiveness of the masks the public will use. The problem we have is there is no hard data on the effectiveness of the masks the public will use. 

“Also, the model itself has 6 parameters (particularly about infectiousness of droplets and spread of different types of infectious material) which were arbitrarily defined. The findings of the model, like all other models, is highly dependent on the assumptions made on these parameters. If any of the assumptions are significantly wrong this will affect the conclusion of the study.”

“A modelling framework to assess the likely effectiveness of facemasks in combination with ‘lock-down’ in managing the COVID-19 pandemic” by Richard Stutt et al. was published in Proceedings of the Royal Society A at 00:01 UK Time Wednesday 10 June.

All our previous output on this subject can be seen at this weblink:

www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.