The two core pillars of the guidelines — that schools should decide whether to open based on community transmission and that students should strive to be spaced 6 feet apart — aren’t supported by science.
While there are many prudent recommendations in the document, these two demands will keep schools closed much longer than necessary, harming kids.
Should learning mode depend on community transmission levels?
The new school opening guidelines advise schools to open or close (or operate in “hybrid” mode) based on a four-tier color-coded system. Each color is tied to the number of new Covid-19 cases during the previous week. The red, or most restrictive category, is more than 100 cases a week per 100,000 people. By this metric, more than 90% of the country is currently in the most restrictive tier, ruling out full-time, in-person learning for elementary-aged students and any sort of in-person school for older children without screening tests.
Yet many schools in such communities already have in-person school — and have done so for months — without issue.
To justify this tiered approach, the CDC guidelines cite a “likely association” between community transmission levels and the risk of exposure in the schools. But the evidence for this is flimsy.
The CDC relies almost exclusively on a U.K. study that examined Covid-19 cases and outbreaks — defined as two or more linked cases — in educational settings in England during June and July. The CDC summarizes the study by noting: “For every 5 additional cases per 100,000 population in regional incidence, the risk of a school outbreak increased by 72%.”
While technically true, that increases is the relative risk, which obscures the study’s key finding about absolute risk: School outbreaks were vanishingly rare in this study —just 0.02% among schools that were open daily during this period — even in areas with high rates of community transmission. And if the CDC had looked at the next figure in the article, focusing on individual infections rather than outbreaks, no association was seen between the number of single infections in school and broader rates of community spread.
The CDC’s school opening guidelines also ignore the experience of at least two U.S. states. Schools in North Carolina and Wisconsin were open during periods of high community transmission (red zone), and both saw far fewer cases in schools than outside of them. The Wisconsin study was published in Morbidity and Mortality Weekly Report, the CDC’s own journal. If the state had taken the CDC’s advice, it never would have done the study in the first place. Moreover, if there is less viral spread in schools than in the community, we want them open precisely during periods of high community spread, when the comparative risks outside of school are highest.
Do schools drive the spread of Covid-19 in the larger community? The CDC guidelines cites two studies. One, using national data, found no overall increase in hospitalization in counties where schools opened this fall, relative to trends during the same period in areas where schools remained closed. For counties with the highest rates of Covid-19 spread when schools reopened, some estimates showed an increase in Covid-19 hospitalizations, but these effects were quite modest, on the order of 2% to 3% above baseline levels of hospitalization. Even if this difference is real, it is quite small and unlikely to overwhelm the health care system unless it is already at the breaking point.
A second study, focused on Michigan and Washington, suggested that schools can contribute to transmission when exiting case counts are high. But this analysis was vulnerable to a classic research problem of reverse causality: school reopening may have led to more frequent testing and detection of infections that would have otherwise gone unrecorded.
Put together, the available evidence offers little reason to believe that in-person learning is particularly risky to students, educators, or people in the community. We believe the benefits of school far outweigh these concerns, and this is especially true as vulnerable people get vaccinated.
Is 6-foot distancing really required?
The CDC guidelines say that schools should try to keep kids 6 feet apart. This guidance, however, appears to be based on decades-old research on the travel distance of large respiratory droplets.
The insistence on 6 feet was controversial from the start. One of the early skeptics was physician Rochelle Walensky, who was recently appointed to lead the CDC. She advised her local school district last summer that “it is quite safe and much more practical to be at 3 feet” as long as everyone is masked. (Three feet of distancing is also recommended by the World Health Organization.)
When asked to explain this about-face during a recent interview with CNN, Walensky argued that the larger distance in the CDC guidance was justified by new research published since last summer and the increase in case counts since then.
The newest evidence actually seems to argue against requiring strict adherence to a 6-foot rule, however. First, it is increasingly clear that transmission of Covid-19 is not explained by the droplet model — the idea that bigger drops of secretion fall in the first few feet around someone, as was thought when the original social distancing guidelines developed. Second, a meta-analysis on Covid-19 and other closely related coronaviruses showed that the benefits of increasing the distance from 3 to 6 feet is marginal in contexts where the risk of infection is low, as would be the case in a classroom with universal masking.
Most on point is a recent study that examined the dynamics of in-school transmission in Ohio. Working with seven school districts that offered in-person learning in late November and early December of last year, near the peak of daily recorded infections in the state, researchers identified all students and teachers who had tested positive. They then repeatedly tested both their close contacts — other students who were exposed for more than 15 minutes at a distance of less than 6 feet — as well as a comparison set of students who kept their distance, including several hundred attending other classes within the same school. The rates of infection among close contacts and students who stayed more than 6 feet away were nearly identical in both elementary and high schools, suggesting minimal value from strict adherence to a 6-foot distancing rule as long as masks are worn consistently and correctly.
Three feet versus 6 might sound trivial, but it really matters. Given the limitation of classroom size, maintaining 6 feet of distance will thwart many schools from operating at full capacity, meaning that students would be able to attend part-time at best, using a hybrid model.
This requirement also complicates transportation. Although the main CDC guidance does not discuss transportation in detail, an accompanying handout advises districts to “skip a row if possible” on school buses. The busing constraint is particularly binding in large urban districts, where many students attend charter or magnet schools far away from their homes and rely on district-provided transportation.
Going backward on reopening
Rather than moving the ball forward on Biden’s goal of getting elementary and middle schools reopened as soon as possible, the new CDC guidelines will work to provide political cover for interest groups and districts that want to delay in-person school.
They also come when many states were acting to loosen their own guidelines to encourage schools to reopen. Just days before the CDC announcement, the state of Massachusetts announced the elimination of school bus capacity limits as long as bus windows remain open at least 2 inches. Nevada, which already allowed closer spacing on school buses, also loosened its requirements further. But, the new CDC guidelines would thwart these pragmatic efforts. The conflicting CDC guidance only creates confusion, putting districts in the difficult position of deciding whether to follow state or federal recommendations.
Most worrisome is that the stringent CDC criteria will likely increase pressure to reduce in-person learning in many places that have been operating at full capacity and with older students. As recent test score data from Ohio show, moving from in-person to hybrid formats will exacerbate learning losses, compounding the both the social and academic harms students have already experienced during the pandemic.
A truly science-based analysis must recognize the difficult tradeoffs involved — including the long-term of interests of children who are most directly affected — and carefully weigh modest increases in Covid-19 infection risk to educators and broader community members against the harms of school closures.
By promoting slavish adherence to arbitrary benchmarks and distancing requirements, the new CDC school opening guidelines do a disservice to science and kids.
Vladimir Kogan is an associate professor of political science at the Ohio State University. Vinay Prasad is a hematologist-oncologist and associate professor of medicine at the University of California, San Francisco.