A World Health Organization-commissioned study was under fire by senior scientists after pointing out the flaws of recent social distance guidelines. They remain concerned about the study being used as evidence to relax the 2-meter social distancing rule in the UK.
The critics are saying that the said 2 meters apart rule is too cautious for suggesting that reducing the distance to 1 meter would only raise possible risk infection from 1.3% to 2.6%. Professor David Spiegelhaler, a Cambridge University statistician and has a role in the government's Scientific Advisory Group for Emergencies, is very suspicious of the new study.
Professor Kevin McConway, an Open University statistician expressed that the analysis 'should not be used in arguments about how much greater the infection risk is at [a] 1-meter minimum distance as opposed to 2 meters. These scientists believe that there is not enough proof for the government to make judgments on what is safe physical distancing.
2-Meter Rule
Criticism followed Prime Minister Boris Johnson's announcement of a formal review of the 2-meter rule by July 4 as businesses are scheduled to reopen next month. For the past few weeks, Johnson had been intensely pressured by the Conservative MPs to lift physical distancing restrictions for the sake of business, especially for the hospitality industry.
It was also reported that the falling numbers of cases, which is probably less than 1000 now, said the Prime Minister. Conservative lawmakers and businesses have said that the UK government can follow a new 1.5-meter rule from other countries so pubs and restaurants can operate with less difficulty.
Researchers from McMaster University in Ontario, released the study earlier this year claiming a systematic review of estimating the risk of infection. Pooled data from previous studies were analyzed to estimate the risk of contracting coronavirus at different distances while considering face masks and eye protection as a means of prevention.
Spiegelhalter questioned authors of the Lancet-published article saying that 'They are forcing the proportional fit to be the same.' The authors assumed that the infection risk from two meters being reduced to one meter is the same as one meter to zero meters.
McConway said 'The method of comparing the different distances in the paper is inappropriate for telling you exactly how the risk at 2-meter minimum distance compares to a 1-meter minimum distance. It does not support, and should not be used in, arguments about how much greater the risk is with a 1-meter limit versus a 2-meter limit.' He believes that there is a problem with how the team compared various distances to determine the risk of infection.
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Absolute Figures
Ben Cowling, a Professor at the WHO Collaborating Centre for Infectious Disease Epidemiology and Control at the University of Hong Kong tweeted his own concerns over the physical distancing study. He even said that he is 'not taking the whole paper very seriously' as it focuses only on distance without considering the duration of exposure.
Not taking the whole paper very seriously. The analysis underlying Fig 3 ignores duration which is just as important as distance for risk of transmission. Risk = f(duration, distance) not f(distance). — Ben Cowling (@bencowling88) June 12, 2020
McConway thinks that the paper was rushed to publication, lacking proper peer-review, and said 'that important things were missed' by the authors, the Lancet peer reviewers, and perhaps even the WHO. With everyone believing that the risk of infection at only one-meter physical distance is higher, "we need to know how much higher because there's a trade-off between the increased risk and the gains from moving to 1-metre. But if you don't know how the risks at 1 meter and 2 meters compare, how do you know how to trade it off? It's finger in the air stuff," he said.
Another recent publication on the correlation between physical distancing and transmission analyzes how effective the 2-meter rule is. The study notes that a 2-meter physical distance 'mitigates droplet and short-range aerosol transmission.' However, the paper also notes that this rule is 'not an absolute figure' and clarifies other factors that need to be considered - duration of people meeting, ventilation, and room size, and that the physical distance 2-meter rule 'should be seen as a ballpark guide to distancing rather than an absolute value.'
A statement by the WHO recommends keeping a distance of at least 1 meter. defending the paper they commissioned, they claimed the study 'was based on a systematic review of all available, relevant observational studies concerning protective measures to prevent transmission of the coronaviruses that cause Sars, Mers, and COVID-19. After checking for relevance, 44 comparative studies done in health-care and non-health-care settings were included.'
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