For all of Harvard’s students to return to in-person learning five days a week, kids will have to be spaced closer than 6 feet apart from one another. There simply isn’t enough room otherwise. Fortunately, our school system has anti-COVID-19 measures in place that will help keep kids, educators, and staff safe even at 3 to 6 feet of distance.
As I discussed in my last column, the 6-foot rule is based on the idea that the coronavirus is transmitted primarily by “large droplets,” which don’t tend to travel farther than 6 feet from unmasked people. But over the past year we’ve learned that COVID-19 is often transmitted via microscopic droplets called aerosols, which can travel farther than 6 feet from unmasked folks and linger in the air for a while.
Fortunately, the past year has also taught us that masks can block not only large droplets, but a high percentage of aerosols, too. And while we know from laboratory research that masks work best when they’re snug and have multiple layers, masking doesn’t have to be perfect to make things better. A December 2020 review in the journal Cell cited seven different papers showing that mask-wearing and mask mandates decrease community infection rates. Real-world evidence like this shows that wearing masks can drastically decrease COVID-19 transmission; and in the real world, not everyone wears a perfect mask perfectly.
One thing that scientists haven’t been able to figure out over the past year is the number of virus particles someone needs to inhale in order to get infected with the virus that causes COVID-19. But no matter what that number is, you’re less likely to reach it if there are fewer of those virus particles in the air around you to begin with. That’s why good ventilation in indoor spaces is so important: It moves virus-contaminated air out and brings fresh, clean air in.
Of course, the best way to keep infectious virus particles out of a room is to prevent contagious folks from entering the room to begin with. Since people can be contagious before they show symptoms—or may never show symptoms at all—another critical layer of protection in the school system is screening folks for COVID-19. This testing is becoming even more crucial now, as more-transmissible variants are gaining prevalence in our area.
Wearing masks, ventilating rooms, and screening people all lower the risk of COVID-19 transmission. Physical distancing decreases the risk even further. But with all those other safety measures in place, the distance between people doesn’t have to be that wide, as was shown by a large meta-analysis published last June in The Lancet, Britain’s premier medical journal. The researchers looked at 172 different studies, which together provided results from more than 25,000 people around the world. That study demonstrated that once your baseline risk of infection is either intermediate or low, moving from 1 meter of distancing (about 3 feet) to 2 meters of distancing (about 6 feet) barely changes your risk.
Last week, a study was published in the journal Clinical Infectious Diseases that provided real-world data complementing The Lancet’s analysis. The study looked at data from 251 Massachusetts school districts, comprising more than 500,000 students and nearly 100,000 teachers and staff members. All the schools required masking; more than 90% had improved their ventilation in some way. There was no significant difference in the COVID-19 case rates of schools at 3 vs. 6 feet of distance.
Schools are not perfect, and they’re not magic. But they’re necessary. We know what we need to do to make schools safe enough for kids and teachers to attend in person; it’s all right here. If we do what we need to do, it’ll work. Even at only 3 feet of distance.
Special thanks to Suzie Clarke Allen, MSN, C-PNP; Melea Atkins, MBA; Andrea Ciaranello, M.D., MPH; and Rosy Hosking, Ph.D, for their assistance in writing this article.
Liz Ruark is the founder of covidsafeschools.org and co-chair of COVID-Safe Schools, Harvard Public Schools’ community COVID-19 screening program. She holds a DVM degree from Tufts Cummings School of Veterinary Medicine.
Harvard Public Schools mitigation strategies
Masks and ventilation
- High quality, well-fitted masks are mandatory for everyone who enters any school building and must be worn properly.
- All eating and drinking up to this point has been done outdoors. Once the schools start serving lunch, they will do so outside whenever possible; in severely inclement weather, lunch will be served in large indoor spaces with good ventilation, such as the gym. Students will be distanced 6 feet or more apart during lunch.
- Bromfield’s HVAC systems have been repaired and filters have been upgraded.
- Classroom windows remain open throughout the school day.
- Air purifying systems are in place in classrooms without windows.
- Voluntary no-cost weekly COVID-19 screening via pooled PCR testing has been available to all in-person students, educators, and staff since January. This weekly testing will continue for the remainder of the school year.
- On average, 75% of students and 70% of educators and staff members are screened each week.
- In nine weeks of testing, only eight positive cases have been detected: a 1.22% in-school test positivity rate.
- No cases of in-school spread have been detected through contact tracing and repeat testing.