June 1 (UPI) -- Staying at least 1 meter -- just over 3 feet -- from other people, as well as wearing face coverings and eye protection, is the best way to prevent spread of COVID-19, an analysis published Monday by The Lancet has found.
Two meters -- about 6 1/2 feet -- is preferred, said researchers who conducted the study to assist the World Health Organization prepare pandemic guidance.
They said, however, that none of the approaches studied -- including social distancing and face coverings -- provides complete protection from the disease caused by the new coronavirus, SARS-CoV-2.
"Our findings are the first to synthesize 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," co-author Dr. Holger Schünemann said in a press release.
"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," said Schünemann, a physician and professor of epidemiology at McMaster University in Canada,
The best available evidence suggests that COVID-19 most commonly is spread by respiratory droplets, especially when people cough and sneeze.
The virus can then enter through the eyes, nose and mouth, either directly or by touching a contaminated surface, Schünemann and his colleagues said.
For the analysis, the researchers reviewed data from 44 studies that assess distancing measures, face masks and eye protection to prevent virus transmission between those with confirmed or probable COVID-19, SARS or MERS infection and individuals close to them.
Like COVID-19, SARS and MERS are diseases caused by coronaviruses.
Analysis of data from nine studies with 7,782 participants looking at social distancing and virus transmission revealed the tactic reduces the risk for spread.
Keeping a distance of more than 1 meter from other people was associated with 3 percent risk for infection, compared with 13 percent for less than 1 meter, the researchers observed.
In addition, modeling conducted by the researchers suggests that for every extra meter of distance up to 3 meters -- or nearly 10 feet -- the risk for infection or transmission is reduced by half.
Meanwhile, 13 studies of all three viruses, with 3,713 participants, that focused on eye protection found that face shields, goggles and glasses reduced risk for infection by more than half, the researchers found.
Evidence from 10 studies of all three viruses with 2,647 participants found similar benefits for face masks in general.
However, Schünemann and his colleagues emphasized that more research focused specifically on the spread of COVID-19 is needed to confirm their findings.
"People must be clear that wearing a mask is not an alternative to physical distancing, eye protection or basic measures such as hand hygiene, but might add an extra layer of protection," said Dr. Derek Chu, an assistant professor of allergy and immunology at McMaster University.
Data from 24 studies of all three viruses with 50,566 participants indicated that most participants found personal protection strategies like social distancing and face coverings "acceptable, feasible and reassuring," said co-author Sally Yaacoub, of the American University of Beruit in Lebanon.
The findings are likely to draw significant attention as many states and cities across the United States begin to reopen after two or three months of COVID-19-related lockdowns, Harvard assistant professor of epidemiology Michael Mina said Monday in a conference call with reporters.
Mina said it was particularly concerning because many businesses and institutions lack the facilities to enable employees, customers and visitors to maintain 6 feet of distancing.
"We don't know if the 6-foot distance piece has to be set in stone if people are wearing masks," said Mina, who has not part of the Lancet study. "If facilities have the space, great, but if people are diligent about wearing masks, we may not need to keep to 6 feet."
As of Monday afternoon, nearly 1.8 million Americans had been diagnosed with COVID-19, according to Johns Hopkins University.
Although several states -- including New York, which has the most cases of any in the country -- are seeing downward trends, while others such as Alabama, California, South Dakota and Virginia are seeing spikes, Johns Hopkins researchers reported.
Many of these same states have recently relaxed lockdown restrictions intended to limit spread of the virus, including, in some cases, social distancing measures.