For the new study, an international group of scientists analysed data from research into the Covid-19, Sars and Mers viruses, involving 7,782 participants.
The risk of infection when people stood more than a metre away from the infected individual was found to be three per cent, and 13 per cent if within a metre.
Professor Holger Schunemann, from McMaster University in Canada, who co-led the research, said: “Our findings are the first to synthesise all direct information on Covid-19, Sars and Mers, and provide the currently best available evidence on the optimum use of these common and simple interventions to help ‘flatten the curve’ and inform pandemic response efforts in the community.
“Governments and the public health community can use our results to give clear advice for community settings and healthcare workers on these protective measures to reduce infection risk.”
The team also analysed 13 studies focusing on eye protection and 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 six per cent, and 16 per cent when not wearing it.
Evidence from 10 studies also found similar benefits for face masks in general, with the risk of infection or transmission when wearing a mask three per cent, and 17 per cent when not wearing one. The study looked mainly at mask use within households and among contacts of cases, and was also based on evidence of low certainty.
Linda Bauld, a professor of public health at the University of Edinburgh, who did not take part in the study, said: “The first and probably the most useful finding is that physical distancing matters.
“There have been plenty of complaints that the guidance in the UK on two meters distance is excessive because it is more than in other countries. But this review supports it.
“Maintaining this distance is likely to reduce risk compared to one metre. Thus, where possible, this is the distance that retailers and employers should use as more premises and workplaces reopen in the future. This is going to be very difficult in some settings, but is important and we’ll all need to get used to maintaining this distance for some months to come.”
Food service providers, pubs and hotels will be able to open from July 4, along with hairdressers, churches and leisure facilities such as cinemas.
The advice makes clear that this last group must “meet the Covid-19 secure guidelines” and, if they cannot do this, they might not be allowed to reopen.
The document says: “Some venues which are, by design, crowded, and where it may prove difficult to enact distancing, may still not be able to reopen safely at this point or may be able to open safely only in part.”