Maintaining a two-metre distance from others is twice as effective at preventing the spread of coronavirus than a one-metre gap, a new study suggests.
Keeping one metre apart reduces the risk of transmission to 2.6%, while a two-metre gap decreases the chance of infection by a further 50% within the community.
According to the analysis published in The Lancet, modelling suggests for every extra metre further away up to three metres, the risk of infection or transmission may halve.
If an individual has Covid-19, standing within one metre of them results in a 13% chance of infection.
In the UK people are advised to keep a distance of two metres from others, but there have been calls to reduce this to 1.5 metres – like in Germany, in order to help the hospitality sector reopen.
Places such as theatres and entertainment venues could be hit hard by the two-metre rule, which would severely restrict the number of patrons allowed inside.
The World Health Organization (WHO) recommends people maintain a distance of at least one metre between each other.
The researchers looked at data from nine studies across Sars, Mers and Covid-19, including 7,782 participants.
According to the researchers from McMaster University in Canada, keeping at least one metre from other people as well as wearing face coverings and eye protection, in and outside of healthcare settings, could be the best way to reduce the chance of viral infection or transmission of Covid-19.
Thirteen studies focusing on eye protection found that face shields, goggles, and glasses were associated with lower risk of infection, compared with no eye covering.
They found that the risk of infection or transmission when wearing eye protection was 6%, and 16% when not wearing eye protection.
Evidence from 10 studies also found similar benefits for face masks in general, with risk of infection or transmission when wearing a mask 3%, and 17% when not wearing a mask.
Evidence in the study was looking mainly at mask use within households and among contacts of cases, and was also based on evidence of low certainty.
For healthcare workers, N95 and other respirator-type masks might be associated with a greater protection from viral transmission than surgical masks or similar, the researchers found.
For the general public, face masks are also probably associated with protection, even in non-healthcare settings, the researchers said.
Co-author Dr Derek Chu, assistant professor at McMaster University, said: “With respirators such as N95s, surgical masks, and eye protection in short supply, and desperately needed by healthcare workers on the front lines of treating Covid-19 patients, increasing and repurposing of manufacturing capacity is urgently needed to overcome global shortages.”
Researchers said that none of these interventions – even when properly used and combined – give complete protection from infection.
They noted the certainty of the evidence around face masks and eye protection is low.
The study, conducted to inform WHO guidance documents, looked at the available evidence from the scientific literature and is the first time researchers have systematically examined the optimum use of these protective measures in both community and healthcare settings for Covid-19.
The authors said their findings have immediate and important implications for curtailing the current pandemic, and future waves, by informing disease models, and standardising the definition of who has been “potentially exposed” for contact tracing.