Student Well-Being What the Research Says

Higher Rates of Delta Infection Projected in Schools With No Mask Mandate or COVID Testing

By Sarah D. Sparks — September 01, 2021 7 min read
Emily Jeter helps her son Eli, a kindergarten student, get his mask on before heading into class at Jenks East Elementary School, Wednesday, Aug. 18, 2021, in Tulsa, Okla.
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If districts don’t tighten COVID-19 protection efforts—and particularly for elementary school students—outbreaks in schools this fall could get ugly, fast.

New, in-review studies suggest that teachers and students will become infected at higher rates, and absenteeism will rise significantly in schools that do not require universal masking and weekly, systemic testing for COVID-19 and where the large majority of children have not already been vaccinated or had the virus.

Moreover, earlier and wider spread of other seasonal respiratory illnesses could make even asymptomatic cases of coronavirus more problematic, infectious disease experts warn.

“School outbreaks will occur in those settings where masks and other mitigation protocols are not in place,” said Tina Tan, pediatric infectious disease specialist at the Ann & Robert H. Lurie Children’s Hospital of Chicago. “Children can get very ill when they get a COVID-19 infection, so the attitude of ‘just let them get sick’ is far from being OK. We need to do everything we can to prevent the children from becoming ill until they are eligible for vaccination.”

Two studies modeling the transmission of COVID in schools this fall have been published in advance of peer review. They use data on what we know about school outbreaks to date and the potential spread of the Delta strain of the virus—considered about twice as contagious as the original virus—to predict what might happen in different scenarios.

However, a sharp rise in school outbreaks has already begun since Delta became the predominant strain of the pandemic in midsummer. Schools nationwide have reported record numbers of new infections and closures due to quarantine, including one Texas district that closed after two teachers died from the disease in the same week.

The American Academy of Pediatrics, which tracks COVID-19 cases among children, found that in the week leading up to Aug. 26, nearly 204,000 new coronavirus cases have been reported among children, marking a 4 percent increase from the previous week. As schools enter the fall semester, the infection rate sits at an eye-popping 6,374 per 100,000 children. Among 12- to 15-year-olds alone, the youngest group eligible for vaccines, the Centers for Disease Control and Prevention finds the infection rate has jumped sevenfold from the start of June, to 168 per 100,000.

Models highlight masking, testing practices

One of the new modeling studies, led by researchers at the University of North Carolina-Chapel Hill, looked at scenarios in which a school had a low, medium, or high number of students and teachers who had already been vaccinated or who had already recovered from the virus. It also looked at the mitigation strategies being used, such as masking and testing.

In one scenario, a school required all students and teachers to wear masks, tested at least half of its students and teachers for the coronavirus each week, and had a population where there was a low level of incoming protection—like an elementary school where no students were old enough to be vaccinated. In that scenario, about 22 percent of susceptible students would become infected by the end of the semester.

But across all scenarios of schools with no universal masking or systemic weekly testing, more than 3 out of 4 students who could get COVID-19, would get sick. The researchers estimated this could mean the difference between 140 lost school days for a school using masking and testing, compared to 210 additional absences in schools that did not.

Chart: A University of North Carloina study modeled the risk of COVID-19 infection for students over the course of a semester using key parameters like: the percentage of students with some incoming immunity, whether the school required universal masking or performed COVID-19 testing.

A separate new study by University of California-Berkeley researchers finds, similarly, that in the highest-risk schools—where only half or less of the school and community have been vaccinated, and without mandatory mask-wearing and systemic testing—a typical elementary school holding in-person classes could see 33 to 65 additional symptomatic infections in a four-month semester, compared to what would be seen among students in remote-only learning, where they could not contract the virus at school.

By contrast, in a region such as the San Francisco Bay Area, which has about a 70 percent vaccination rate and has reopened with universal masking and other mitigation strategies, the Delta variant could have a much smaller impact. In that case, there could be eight to 36 new students with symptomatic COVID-19 in a typical elementary school, 13 more cases in a typical middle school, and three more cases per high school, compared to the risk of infections for those in remote-only learning.

Rates of teacher infections would be similarly split. The researchers also found scenarios in which schools that also kept students separated into small cohorts would have the lowest infections compared to remote learning.

In part, the rapid spread of COVID-19 predicted in the studies is driven by the inability to vaccinate students under age 12 and the low take-up of vaccinations among older students. As of Sept. 1, the CDC reports 37 percent of 12- to 15-year-olds and just over 46 percent of those 16-17 have been fully vaccinated against COVID-19.

The more infectious a virus is, the more people in a community need to be vaccinated to create a buffer to stop transmission to those who are not vaccinated. While Delta is not as contagious as, say, the measles—one person infected with Delta on average infects seven to nine others without intervention, compared to the typical 12-18 infected by someone with the measles—it’s not yet clear how much greater a portion of a school’s community will need to have immunity from the Delta coronavirus in order to create herd immunity against an outbreak.

“The reality of the situation is that the closer we get to 100 percent, the better off we are,” said John Newland, doctor and professor of pediatrics and infectious diseases at Washington University School of Medicine in St. Louis, Mo. “While I don’t know the number [for herd immunity against the Delta strain], what I do know is that we have a country that has a vaccination rate of around 50 percent, 52 percent [of U.S. adults] … and that’s just not enough. That’s what we get with flu vaccine. We’ve got to do better with COVID-19.”

Schools must emphasize: keep sick kids home

The new research highlights the need for systemic testing on top of masking, as children and those with the Delta strain are each more likely to develop asymptomatic but infectious cases of COVID-19, according to Kristina Bryant, a pediatrician and professor of pediatrics at the University of Louisville and Norton Children’s Hospital who is also a member of the Society for Healthcare Epidemiology of America.

“One mitigation strategy that we really don’t talk about is staying home when you’re sick, and that is really important,” Bryant said. “It’s totally understandable that parents need to go to work and kids need to be in school, and a couple of years ago we might not have kept kids home with symptoms of a mild viral illness.”

But she added, “COVID-19 in many respects looks like every other viral infection in children. And if you say, can it cause wheezing, just like RSV? Yes, it can. Can it cause a barky cough like croup? Yes, it can,” Bryant said.

Administrators should be systemic in testing and conservative in asking parents to keep students home if they seem sick, she said.

Noelle Ellerson Ng, the associate executive director of AASA, the School Superintendents Association, said the pandemic has “blown wide open” the need for better child-care supports across the nation, and that school districts and local employers both have roles to play in creating a better educational and social safety net for families who need to keep their children home to quarantine.

“We are seeing growing dialogue [among district leaders] around what is or isn’t in place for a city for remote-learning options for families that do take the responsible path to quarantine when they expect exposure or when they have to quarantine because of a confirmed case. And there’s always room to do better,” she said.

Though separate, large-scale studies of school mitigation strategies in North Carolina and elsewhere were done before Delta became the dominant strain, Bryant said their findings also offer a roadmap to school districts in planning how to start their school years safely.

“In North Carolina and in some other states, schools opened when there was higher virus [infection rates] circulating in the community and kids were getting infected in the community, but when it came to school, they didn’t transmit it,” Bryant said. “I think time will tell, things could be different with Delta, but for now the data that we have suggested that when layered mitigation strategies were in place, then in-school transmission was minimal.”

A version of this article appeared in the September 08, 2021 edition of Education Week as Higher Rates of Delta Infection Projected for Fall


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