Coronavirus social distancing: 2m vs 1m - what does the science say?

Prime Minister Boris Johnson has announced a reduction in the social distancing rule from two metres to "one metre-plus" in England.

The change will make it easier for businesses to re-open and boost the country’s economy, as it will allow restaurants to operate more covers and hairdressers, pubs and bars can reopen their doors, along with other social settings.

The PM faced growing pressure from MPs and businesses to reduce the distance rule, as part of steps to gradually ease the coronavirus lockdown.

But what does the science say about the reduction – is it safe?

And what social distancing rules are in place in other countries?

• What is 'one metre plus'?

The two-metre social distancing rule is being reduced to “one metre-plus” in England from July 4, to aid the return of restaurants and pubs from the same day.

But people are advised to still keep a distance of two metres, where possible.

"One-metre plus" involves keeping one metre apart, plus other mitigations such as wearing face coverings, sitting people side to side rather than face to face to reduce transmission, and increased use of hand sanitiser.

Unveiling the relaxation of social distancing measures, Mr Johnson said: “Where it is possible to keep two metres apart, people should.

“But where it is not, we will advise people to keep a social distance of one metre-plus, meaning they should remain one metre apart while taking mitigations to reduce the risk of transmission.”

• Why do we have a social distancing rule?

Quite simply, to help stop the transmission of coronavirus.

The virus can be spread via droplets released when an infected person coughs, sneezes or breathes.

Under the current rule, people are urged to stay two metres apart from those they don’t live with, to prevent potential infection, but this will change to "one metre-plus" from July 4.

Regularly washing hands and wearing face masks are other measures that can help limit the spread of the virus.

• What does the science say?

Scientists have argued that the risk of exposure to coronavirus reduces with increased physical distance.

The government’s Scientific Advisory Group for Emergencies (Sage) say current evidence is that a one metre distance could carry between two and 10 times the risk of two metres.

If social distancing is reduced to less than two metres then other mitigations should be in place to allow people to be closer together, such as limiting duration of contact and face coverings, Sage says.

Dr Shaun Fitzgerald, of Cambridge University, spoke of the measures which could help in a pub setting, as social distancing is reduced.

“Maybe this is an example where face coverings will be an opportunity to reduce transmission risk of droplets,” Dr Fitzgerald told ITV News.

“But if you’re paying by your phone, it reduces the contact risk by handing money over as well.

“Hitting as many of these transmission avenues as possible is a really good way of making these environments safer.”

However Dr Zeshan Qureshi, of University College London, told ITV News the reduction in social distancing will be happening in some of the “highest risk settings”, such as pubs and restaurants.

“The problem with what the government is suggesting is that social distancing is potentially being reduced in some of the highest risk settings for coronavirus transmission, actually we might have to fundamentally rethink how these social interactions happen,” he said.

Professor Christina Pagel told ITV News she believes it’s too early to reduce social distancing measures, and pointed to the Sage advice.

“If you put that into the context of indoors being 19 times riskier than outdoors, according to a Japanese study and then things like prolonged contact, face to face, talking loudly, laughing, all of this is a riskier environment that we’re adding all at the same time, by opening up these social indoor spaces,” she said.

The World Health Organization (WHO) recommends keeping a minimum distance of at least one metre, which some countries have already been following.

“When someone coughs, sneezes, or speaks they spray small liquid droplets from their nose or mouth which may contain virus,” the WHO says.

“If you are too close, you can breathe in the droplets, including the Covid-19 virus if the person has the disease.”

• Professor Christina Pagel says it's too early to reduce social distancing measures

• What is the latest research?

A review from the Centre for Evidence-Based Medicine at Oxford University, led by Dr Qureshi and Professor Lydia Bourouiba released on Monday, concluded the two metre rule was based on an outdated model.

It found the two metre rule assumes viral transmission in either large droplets or small airborne particles.

In reality coronavirus “may be present and stable in a range of droplet sizes, which will travel across a range of distances, including some beyond two metres".

The review recognises that increasing physical distance decreases the risk of transmission of the virus, so easing restrictions from two to one metre may result in a significant increase in risk if other measures are not taken.

Social distancing should be used in combination with other measures to reduce risk of transmission.

A study published in the medical journal The Lancet found the risk of being infected is estimated to be 13% within one metre but only 3% beyond that distance.

It said that the risk of infection is roughly halved with each extra metre of distance.

However the study has been criticised by experts, who say research papers are being written, reviewed and published too fast for sufficient quality checks to be performed.

Prof Kevin McConway, an applied statistician at the Open University, said the studies that formed the basis of the report were varied and were “done for various purposes, with different groups of people in different countries, and put together to try to get average measures of the effects of distancing.

“At best all you’d have got from putting them together was an average across a lot of very different situations in different countries, many of which would be nothing like the situation of people moving around or working in UK towns and cities, and arguably it might not even make enough sense to relate this average to specific distances like one metre or two metres,” Prof McConway told ITV News.

• What mitigations should be put in place?

Scientists agree social distancing should always be accompanied by other mitigations, such as face coverings, but even more so when social distancing is reduced.

Mitigations include hand washing, regular surface cleaning, PPE, face coverings where appropriate, air hygiene and self-isolation of affected people.

The circulation of fresh air and a well-ventilated room is an important way to reduce the risk of infection.

“A big thing for me regarding the internal environment is making sure that it is really well ventilated, to then draw air through the space is really, really helpful to reduce the overall concentration of any virus particles that might be in the air,” Dr Fitzgerald said.

• What social distancing measures are in place in other countries?

Spain still has a two-metre rule in place, but in closed areas and on the street where a two metre distance is not possible, then face masks are compulsory.

In Germany, people should keep a distance of 1.5 metres when in public, whereas in France, Denmark and Singapore, it’s 1m and in the US, it’s 1.8m.

And in Italy, where the virus spread rapidly, a 1.5m social distance measure remains in place.