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Six-Foot Rule for Preventing the Spread of COVID-19 is Likely Useless, MIT Researchers Find

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New MIT research challenges COVID-19 restrictions, showing that the commonly used social distancing rule does not have a scientific foundation

New peer-reviewed research published April 26, 2021, shows that one of the foundational concepts used to prevent the spread of COVID-19 during the global pandemic does not seem to have a scientific foundation. Massachusetts Institute of Technology (MIT) researchers examined the efficacy of social distancing guidelines in preventing the spread of SARS-CoV-2 and found that while mask-wearing, ventilation, and exposure time significantly impacted the spread of infection, the distance between individuals did not.

We argue there really isnt much of a benefit to the 6-foot rule, especially when people are wearing masks,” Martin Z. Bazant, MIT professor and lead author of the study said in a recent interview. It really has almost no physical basis because the air a person is breathing while wearing a mask tends to rise and comes down elsewhere in the room so youre more exposed to the average background than you are to a person at a distance.”

Testing the 6-Foot Rule in Social Distancing

Martin Bazant research challenges COVID-19 crowd rules
Martin Z. Bazant is an MIT professor and lead author of a new study challenging the 6-foot COVID-19 social distancing rule. He says there is no scientific foundation. (Photo source: MIT.edu)

Surprisingly, the basic science behind the 6-foot rule for COVID-19 spread mitigation has never really been empirically tested. This emphasis on distancing has been really misplaced from the very beginning,” Bazant explained. “The CDC or WHO have never really provided justification for it, theyve just said this is what you must do and the only justification Im aware of is based on studies of coughs and sneezes, where they look at the largest particles that might sediment onto the floor.”

According to Bazant’s team’s research, poorly ventilated spaces where people spend long amounts of time together create the highest degree of risk, regardless of distancing. Unfortunately, the nursing home is one of those cases,” Bazant said. “If Covid patients are living together 24/7, in some cases even in the same room, that is the absolute worst-case scenario, especially given the vulnerability of that population.”

An example of a large ventilated space that Bazant used was university classrooms. Often times the space is large enough, the ventilation is good enough, the amount of time people spend together is such that those spaces can be safely operated even at full capacity and the scientific support for reduced capacity in those spaces is really not very good,” Bazant explained. I think if you run the numbers, even right now for many types of spaces youd find that there is not a need for occupancy restrictions.”

MIT Research Challenges Indoor and Outdoor COVID-19 Crowd Restrictions

Ultimately, the new research shows that social distancing is not particularly useful. The distancing isnt helping you that much and its also giving you a false sense of security because youre as safe at 6 feet as you are at 60 feet if youre indoors and the air is getting well mixed. Everyone in that space is at roughly the same risk, actually,” Bazant continued.

One important finding of the MIT study is that social distancing outside is particularly unhelpful. Air follows the path of least resistance and often times with many masks, thats straight up,” Bazant said. Exhaled air is obviously much warmer than the background and tends to rise. Thats the main reason that distancing outside makes almost no sense, and especially with masks, its even kind of crazy because youre really not going to transmit to someone at 6 feet.

If you look at the air flow outside, the infected air would be essentially swept away and very unlikely to cause transmission,” Bazant added. “There are very few recorded instances of outdoor transmission. Crowded spaces outdoor could be an issue, but if people are keeping a reasonable distance of like 3 feet outside, I feel pretty comfortable with that even without masks.”

Reconsidering COVID-19 Spread Mitigation Measures in the Lab

Ultimately this research shows that the 6-foot rule should not be a core component of COVID-19 spread mitigation strategies. Our study indicates that the six-foot rule is insufficient to limit indoor airborne transmission of COVID-19: one must also limit the time spent in an indoor space,” Bazant explained. “Our study demonstrates how this time limit depends on the relevant factors, including room ventilation and filtration and face-mask use,” they said, noting that face masks can be an extremely effective indoor safety measure.”

Clinical laboratories often advise businesses, schools, and other entities on how to protect those using their services. Clinical laboratories also have to consider ways to prevent the spread of COVID-19 in their clinical settings. Research showing that social distancing is likely inefficacious can help clinical laboratories to focus on recommending interventions that were found to be more effective while avoiding potentially cumbersome and unnecessary social distancing requirements.

—By Caleb Williams, Editor, STAT Intelligence Briefings

Related Resources:

Proceeding of the National Academy of Sciences of the United States of America: A guideline to limit indoor airborne transmission of COVID-19

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