3 feet or 6? Distancing guideline for schools stirs debate
By Emily Anthes
The Centers for Disease Control and Prevention is clear and consistent in its social distancing recommendation: To reduce the risk of contracting the coronavirus, people should remain at least 6 feet away from others who are not in their households. The guideline holds whether you are eating in a restaurant, lifting weights at a gym or learning long division in a fourth-grade classroom.
The guideline has been especially consequential for schools, many of which have not fully reopened because they do not have enough space to keep students 6 feet apart.
Now, spurred by a better understanding of how the virus spreads and a growing concern about the harms of keeping children out of school, some public health experts are calling on the agency to reduce the recommended distance in schools to 3 feet from 6.
“It never struck me that 6 feet was particularly sensical in the context of mitigation,” said Dr. Ashish Jha, dean of the Brown University School of Public Health. “I wish the CDC would just come out and say this is not a major issue.”
On Sunday, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said on CNN that the CDC was reviewing the matter.
The idea remains contentious, in part because few studies have directly compared different distancing strategies. But the issue also boils down to a devilishly difficult and often personal question: How safe is safe enough?
“There’s no magic threshold for any distance,” said Dr. Benjamin Linas, a specialist in infectious diseases at Boston University. “There’s risk at 6 feet, there’s risk at 3 feet, there’s risk at 9 feet. There’s risk always.” He added, “The question is just how much of a risk? And what do you give up in exchange?”
The origins of 6 feet
The origin of the 6-foot distancing recommendation is something of a mystery. “It’s almost like it was pulled out of thin air,” said Linsey Marr, an expert on viral transmission at Virginia Tech University.
When the virus first emerged, many experts believed that it was transmitted primarily through large respiratory droplets, which are relatively heavy. Old scientific studies, some dating back more than a century, suggested that these droplets tend not to travel more than 3 to 6 feet. This observation, as well as an abundance of caution, may have spurred the CDC to make its 6 foot suggestion, Marr said.
But that recommendation was not universal. The American Academy of Pediatrics recommends 3 to 6 feet of social distancing in schools, but the World Health Organization recommends just 1 meter, or 3.3 feet.
And over the past year, scientists have learned that respiratory droplets are not the primary mode of coronavirus transmission. Instead, the virus spreads mostly through tiny airborne droplets known as aerosols, which can travel longer distances and flow through rooms in unpredictable ways.
Data also suggests that schools appear to be relatively low-risk environments; children under 10 seem to transmit the virus less readily than adults.
“One of the really important data points that has been missing is a direct head-to-head comparison of places that had implemented 3 feet of distance versus 6 feet of distance,” said Dr. Elissa Perkins, director of emergency medicine infectious disease management at Boston University School of Medicine.
A natural experiment
Perkins and her colleagues recently conducted such a comparison by taking advantage of a natural experiment in Massachusetts. Last summer, the state’s education department issued guidelines recommending 3 to 6 feet of distancing in schools that were planning to reopen in the fall. As a result, school policies varied: Some districts imposed strict 6-foot distancing, whereas others required just 3. (The state required all staff members, as well as students in second grade and above, to wear masks.)
The researchers found that the social distancing strategy had no statistically significant effect on COVID-19 case rates, the team reported in the journal Clinical Infectious Diseases last week. The study also found that COVID-19 rates were lower in schools than in the surrounding communities.
The authors say the findings provide reassurance that schools can loosen their distancing requirements and still be safe, provided they take other precautions, like enforcing universal mask wearing.
“Masking still appears to be effective,” said lead investigator Dr. Westyn Branch-Elliman, an infectious diseases specialist at the VA Boston Healthcare System. “And so, provided we have universal masking mandates, I think it’s very reasonable to move to a 3-foot recommendation.”
Not everyone finds the study so convincing. A. Marm Kilpatrick, an infectious disease researcher at the University of California, Santa Cruz, said that the school-district data was too noisy to draw firm conclusions from. “It doesn’t really allow you to get, I think, an answer that you can feel really confident in,” he said.
The study’s authors acknowledged that they could not rule out the possibility that increased distancing provided a small benefit.
With aerosol transmission, safety generally increases with distance; the farther the aerosols travel, the more diluted they become. “It’s like being close to a smoker,” Marr said. “The closer you are, the more you’re going to breathe in.”
Debate and diminishing risks
Some experts say that a small increase in risk is outweighed by the benefits of fully reopening schools. “Trying to follow the 6-foot guideline should not prevent us from getting kids back to school full time with masks, with at least 3-foot distancing,” Marr said.
Others said it was too soon to loosen the CDC guidelines. “Ultimately, I think there could be a place for this changing guidance,” Saskia Popescu, an infectious disease epidemiologist at George Mason University, said in an email. “But it’s not now, when we are struggling to vaccinate people, we’re still seeing over 60,000 cases a day and we’re trying to not reverse the progress we’ve made.”
Even proponents of changing the guideline say that any shift to looser distancing will have to be done carefully, and in combination with other precautionary measures. “If you’re in an area where there’s not a strong tendency to rely on masks, I don’t think it would be wise to extrapolate our data to that environment,” Perkins said.