Physical distancing, face masks and eye protection, do they prevent person-to-person transmission of SARS-CoV-2 and COVID-19?

A review published in The Lancet by Derek Chu and others June 1, 2020.

The authors aimed to investigate the effects of physical distance, face masks and eye protection on virus transmission in the healthcare and non-healthcare settings.

They undertook a systematic review and meta-analysis to investigate the optimum distance for avoiding person-to-person virus transmission and to assess the use of face masks and eye protection to prevent transmission of viruses. 

They obtained data from 21 standard WHO specific and COVID-19 specific sources looking at SARS-CoV-2, other betacoronaviruses causing severe acute respiratory syndrome and the Middle East respiratory syndrome, MERS. 

They searched the data sources from database inception to May 3, 2020.  They rated the certainty of evidence according to the Cochrane methods and GRADE approach.

They looked at 172 observational studies across 16 countries and 6 continents. 

Transmission of viruses was lower with a physical distancing of 1 metre or more, compared with a distance of less than 1 metre.  They found that protection was increased as distance was lengthened. 

Face mask use resulted in a large reduction in the risk of infection with stronger associations with N95 or similar respirators compared with disposable surgical masks or similar.

Eye protection was also associated with less infection. 

They concluded that the findings of their systematic review supported physical distances of 1 metre or more.  Their findings also supported the use of face masks, respirators and eye protection in public and healthcare settings. 

They suggested that robust randomised trials were needed but best available current evidence suggested their use.

The findings from this study showed a reduction in risk of 82% with a physical distance of 1 metre in both healthcare and community settings.  Every additional 1 metre of separation more than doubled the relative protection, with data up to 3 metres.  The 1 to 2 metre distance rule in most hospital guidelines is based on out-of-date findings from the 1940s with studies from 2020 showing that large droplets can actually travel as far as 8 metres. 

Chu and colleagues have reported that masks and respirators reduce the risk of infection by 85%.  Eye protection resulted in a 78% reduction in infection, suggesting that infection via the ocular route might occur by aerosol transmission or self-inoculation.  Chu and colleagues also reported that respirators and multilayer masks were more protective than single layer masks.  This is an important finding and should inform those who are making home-made cloth masks, many of which are single-layered.  A well-designed cloth mask should have water-resistant fabric, multiple layers and a good facial fit.

The study has supported the use of universal face masks, because masks were equally effective in both healthcare and community settings.  The growing evidence for both presymptomatic and asymptomatic transmission of SARS-CoV-2 further supports universal face mask use and distancing. 

Universal face mask use might enable the safe lifting of restrictions in communities trying to resume normal activities and therefore could protect people in crowded public settings and within households. 

They also concluded that not one intervention was completely protective and a combination of physical distancing, face mask use and other interventions were needed to mitigate the COVID-19 pandemic until an effective vaccine was developed.  This study provides the very best specific evidence for COVID-19 prevention.

The London General Practice has kept abreast of all aspects of SARS-CoV-2 and COVID-19 infection.  In the practice setting, it has transformed the office to accommodate social distancing, the wearing of face masks and gloves and this has resulted in the ability to see patients face-to-face who do not have florid COVID symptoms.  All our doctors wear appropriate PPE and all patients are triaged prior to their arrival.  We are fortunate in having three waiting areas and there is no intermingling of patients within a 2 metre rule. 

If you have any medical concerns, please do not hesitate to contact us.

The London General Practice

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