Face coverings can help control Covid-19 transmission in the community but they should not be a replacement for other coronavirus measures such as social distancing, scientists have said.
In a new modelling study, researchers in the US have found a 10% rise in self-reported mask wearing to be associated with a three-fold increase in the odds of keeping the reproduction number R below 1.
R is the number of people that one infected person, on average, will pass on the virus to. When the R value is above 1, it means the epidemic is growing.
The experts said their findings, published in the journal Lancet Digital Health, suggest that communities in the US with high reported mask-wearing as well as physical distancing have the highest predicted probability of transmission control.
This research provides additional evidence that those interventions should include wearing face masks to protect ourselves and as well as physical distancingStudy co-author Dr Christina M Astley
Ben Rader, of Boston Children’s Hospital and Boston University in the US, who is a co-author on the study, said: “An important finding of this research is that mask wearing is not a replacement for physical distancing.”
The researchers used a web-based survey to gather data on face-covering habits from more than 300,000 people in the US between June 3 and July 27 2020.
They also used anonymised data from Google users who had opted to allow sharing of their location history on their mobile devices alongside information gathered from other Covid-19 tracking projects.
However, the researchers stress their study only provides a link between wearing of face coverings and slowing down virus transmission, and cannot prove a direct cause-and-effect.
They said it is possible that people who report wearing face coverings may also engage in other behaviours that reduce their risk of Covid-19 infection, such as increased hand washing, which was not addressed in the study.
Dr Christina M Astley, a clinician and epidemiologist with Boston Children’s Hospital and Harvard Medical School, and study co-author, said: “Our findings suggest widespread use of face masks may help to control Sars-Cov-2 (the virus that causes Covid-19) transmission.
“The world is facing a more transmissible coronavirus strain, hospitals are struggling with new cases and vaccination programmes are still being rolled out.
“Interventions are needed now to lower the burden on our healthcare systems.
“This research provides additional evidence that those interventions should include wearing face masks to protect ourselves and as well as physical distancing.”