Masks, ventilation upgrades lowered COVID-19 incidence in elementary schools
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Mask requirements and upgrades to ventilation reduced the incidence of COVID-19 in Georgia elementary schools by up to almost half, data published in MMWR showed.
Dilution methods, such as opening windows and doors and using fans, lowered the incidence by 35% when used alone, according to Jenna Gettings, DVMMPH, a CDC Epidemic Intelligence Service officer embedded with the Georgia Department of Public Health, and colleagues. With the addition of high-efficiency particle-absorbing filters, the incidence was reduced by 48%.
The researchers found that the incidence was 37% lower in schools that required mask use among teachers and staff members.
‘Multifaceted’ approach
The study data came from a survey of 169 elementary schools that opened for in-person learning in Georgia. The data were from a 26-day period from Nov. 16 to Dec. 11, 2020.
The COVID-19 incidence rate for all schools combined was 3.08 cases per 500 enrolled students. The community incidence rate in counties with schools participating in the study was 1,055 per 100,000 people — or approximately 5.28 per 500 persons, the authors reported.
Those schools that implemented dilution methods alone (39 schools) had 2.94 cases per 500 students (RR = 0.65; 2.94 [95% CI, 2.48-3.5]). Those that implemented only filtration upgrades (16 schools) had 2.46 cases per 500 students (RR = 0.69; 2.46 [95% CI, 1.84-3.29]). For schools that implemented both dilution methods and filtration upgrades (31 schools), there were 2.22 cases per 500 students (RR = 0.52; 2.22 [95% CI, 1.73-2.84]).
“Preventing transmission of SARS-CoV-2 in schools should be multifaceted,” the authors wrote. “Mask requirements for teachers and staff members and improved ventilation are important strategies that elementary schools could implement as part of a multicomponent approach to provide safer, in-person learning environments until vaccines are available for children aged younger than 12 years.”
High school testing
In a second study published in MMWR, Cdr. William A. Lanier, DVM, MPH, DACVPM, a senior epidemiologist at the USDA Food Safety and Inspection Service, and colleagues assessed two Utah high school COVID-19 testing programs that aimed to sustain extracurricular activities and in-person instruction.
The first, called “Test to Play,” mandated testing every 14 days for students wanting to participate in extracurricular activities. The second, called “Test to Stay,” was mandatory to continue in-person instruction.
“Test to Play” was implemented in 127 of Utah’s 193 public high schools, whereas “Test to Stay,” was implemented at 13 high schools. For both programs, the Utah Department of Health provided training and rapid antigen test kits to staff members, who performed school-based testing. Parental permission was required for students to receive testing.
From Nov. 30, 2020, to March 20, 2021, 1,886 (3.2%) of 59,552 students participating in one of the two programs received a positive test result, the researchers reported. Those who tested positive were required to isolate for 10 days from the date of test.
Lanier and colleagues said the programs “facilitated the completion of approximately 95% of high school extracurricular competition events and saved an estimated 109,752 in-person instruction student-days.”
“Utah’s high school COVID-19 testing programs saved in-person instruction days and facilitated continuation of extracurricular activities in accordance with statewide public health policy during a period of high COVID-19 incidence among persons of high-school student age,” they wrote.
“Growing evidence suggests that when schools implement recommended prevention strategies, including consistent and correct use of masks, physical distancing, hand hygiene, and room ventilation improvements, in-school COVID-19 transmission is infrequent, while loss of in-person instruction can have detrimental effects on children’s education and their social and emotional well-being.”
References:
Gettings J, et al. MMWR Morbid Mortal Wkly Rep. 2021;doi:10.15585/mmwr.mm7021e1.
Lanier WA, et al. MMWR Morbid Mortal Wkly Rep. 2021;doi:10.15585/mmwr.mm7021e2.
Perspective
Back to TopLinsey Marr, PhD
The first study provides real-life evidence validating the benefits of masks, ventilation and filtration in reducing COVID-19 transmission. We know from fundamental scientific principles that these three interventions should work, like we know that gravity means that an apple will fall from a tree rather than float off into space. Masks, even if not as good as an N95 and even if not worn perfectly, will reduce the amount of virus an infected person releases into the air around them and will also reduce the amount of virus other people breathe in from the surrounding air. Ventilation and filtration reduce the amount of virus in the air. Interestingly, the study found no association between distancing of at least 6 feet and disease incidence, nor between use of barriers and disease incidence. In sum, these results provide further evidence that COVID-19 is transmitted mainly through aerosols. If it were transmitted mainly by large droplets, then we would expect to see a benefit of masks, distancing and barriers, but not of ventilation and filtration.
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