The “most comprehensive study to date” found that physical distance and perhaps wearing a mask were the two best ways to prevent transmission of the new coronavirus.
The new study, published in the Lancet medical journal on Monday, found that people should stay at least three feet away and longer if possible.
The review of several published studies, paid for by the World Health Organization, had three main findings:
The researchers analyzed 172 observational studies in 16 countries and six continents, including studies in healthcare and community settings. They did not analyze randomized controlled trials, considered the gold standard, but almost impossible to implement to study the transmission of infections in people.
Researchers from universities around the world looked at studies of the outbreaks of Covid-19, the SARS virus, and the Middle East respiratory syndrome virus (MERS), which are from the same family of viruses.
‘Big step forward’
The results of the review support a physical spacing policy of at least 1 meter (3.3 feet) and, if possible, 2 meters (6.6 feet) or more, the researchers said. The information could also be used to inform models that predict the spread of the disease and help with contact location schemes, added the research team, led by Holger Schünemann of McMaster University in Canada.
Trish Greenhalgh, a professor of Primary Care Health Services at Oxford University who was not involved in the research, said that while all of these results were subject to uncertainty, the overwhelming message is that physical measures are effective in preventing Covid-19. .
“This is a great step forward in our knowledge, since the previous meta-analyzes were mainly based on the prevention of influenza and other diseases, which do not behave in the same way as the Covid-19 virus,” he told the Science Media Center. in London.
“On all three questions, the evidence seems to support the measurements. For example, staying 1 meter away from other people on average seems to reduce the chance of catching Covid-19 by 80%. Wearing a mask or covering your face seems reduce your risk by up to 85%. And wearing glasses or a face shield seems to reduce it by up to 78%. “
Tarik Jašarević, a WHO spokesman, said the international health agency was in the process of updating its advice on wearing masks, with a change likely to be announced this week.
The changes are likely to touch the best materials to make masks, based on recent data from the United States, “he told CNN by email.
“The WHO has maintained a focus on the use of masks where there is evidence that they can limit transmission, such as in healthcare settings. In fact, the new guideline may expand its use in these settings,” he added.
Next steps for government leaders
The key question now was how governments and the public should interpret these results, said Linda Bauld, a professor of public health at the University of Edinburgh.
“The first and probably the most useful finding is that physical distance is important. There have been many complaints that orientation in the UK at a distance of 2 meters is excessive because it is more than in other countries,” he told Science Media. Center.
“But this review backs it up. Keeping this distance is likely to reduce risk compared to 1 meter. So wherever possible, this is the distance that retailers and employers should use as more are reopened. premises and workplaces in the future. “
Bauld added that while the certainty of the evidence was low on face masks, making it difficult for governments to make them mandatory, the review added to the evidence that leaders should ask the public to wear face covers on public transportation. , in stores and other Interior spaces, even when physical distancing is in place, he said.
For healthcare workers, the study found that N95 masks and other respirator-type masks could provide greater protection against viral transmission than surgical masks or multi-layered cotton or gauze masks.
However, the review did not examine the effects of wearing masks to protect other people, Greenhalgh of Oxford noted. She said the general public should wear either a cloth mask or a standard surgical mask, leaving respirator masks for healthcare workers.
Even when used and combined properly, spacing, masks and eye protection do not offer complete protection, the study emphasized, and basic measures such as hand washing are essential to reduce transmission.