‘My facemask protects you, your facemask protects me’

Increasingly, several studies are revealing the crucial role that facemasks play in reducing the spread of Covid-19. The latest one, published on June 10 by British researchers, employs two mathematical models. The first simulates the consequences of wearers using facemasks after the onset of symptoms. The second model uses free-living SARS-CoV-2 particles to weigh the impact of a combination of facemasks and varying degrees of lockdown. The researchers show that if facemasks are used by the public before Covid-19 symptoms appear, the effective reproduction number, R0 (or R-nought), can be brought below 1. The report states that even basic homemade masks can significantly slash transmission if more people wear them outdoors. The team also probed the effectiveness of various types of masks. The lead author of the study, Dr Richard Stutt, who is part of Cambridge’s Department of Plant Sciences, spoke to Open about the findings published in the research journal,Proceedings of the Royal Society A. Edited Excerpts:

Why did it take so long for medical researchers to come out with a comprehensive study of the benefits of wearing facemasks?

I don’t have any inside information on policy decisions for governments and the WHO, so I can’t help with insight into their decision processes. I can say that establishing a scientific evidence base for masks has taken time, as it is difficult to perform experiments or gather the necessary information from outbreaks. There has also been the perception that masks cannot offer total protection, and this is one of the things we address in our paper: masks can still provide significant benefits in slowing the rate of spread and controlling the outbreak at the population level, even if masks are not perfect.

Could you elaborate on the significance of this study as we enter advanced stages of infection and lockdown?

Our study does not directly establish the effectiveness of masks, we rely on experiments and data from other sources to inform us. For instance, Germany experienced a 40% reduction in infection rate following the introduction of mandatory mask wearing . Another one was the HKU animal trial in which surgical masks reduced infection rates by 50% to 75%.

We would say that a key thing to remember is masks are just as much about preventing infected people from spreading the virus as they are about directly protecting healthy people. We recommend wearing masks all the time, particularly due to the Covid-19 featuring a pre-symptomatic infectious phase in which people may be unaware that they are ill but still spreading the virus. As my coauthor John Colvin says: “My mask protects you, your mask protects me”.

What kind of facemasks do you recommend that people wear to combat the pandemic? 

We would recommend medical-grade facemasks wherever possible, but these should be reserved for healthcare professionals if there are shortages. We would recommend well designed and fitted homemade cloth masks where medical masks are not available. The German data indicates that homemade masks are still providing significant benefits at the population level.

What is your advice to governments that are still grappling with high rates of infections and are struggling to flatten the curve?

We believe that the best results are achieved when facemasks are combined with other interventions such as social distancing and good hygiene practices. Combining interventions has a better outcome than any one intervention. Lockdowns have also proven effective with good compliance, and can be combined with other interventions to control the most serious outbreaks.

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