When officials closed US schools in March to limit the spread of COVID-19, they may have prevented more than 1 million cases over a 26-day period, a new estimate published online this week in JAMA suggests.
But school closures also left blind spots in understanding how children and schools affect disease transmission.
“School closures early in pandemic responses thwarted larger-scale investigations of schools as a source of community transmission,” researchers noted in a separate study published online July 30 in JAMA Pediatrics that examined levels of viral RNA in children and adults with COVID-19.
“Our analyses suggest children younger than 5 years with mild to moderate COVID-19 have high amounts of SARS-CoV-2 viral RNA in their nasopharynx compared with older children and adults,” report Taylor Heald-Sargent, MD, PhD, and colleagues. “Thus, young children can potentially be important drivers of SARS-CoV-2 spread in the general population, as has been demonstrated with respiratory syncytial virus, where children with high viral loads are more likely to transmit.”
Although the study “was not designed to prove that younger children spread COVID-19 as much as adults,” it is a possibility, Heald-Sargent said in a related news release. “We need to take that into account in efforts to reduce transmission as we continue to learn more about this virus.” Heald-Sargent is a pediatric infectious diseases specialist at Ann & Robert H. Lurie Children’s Hospital and assistant professor of pediatrics at Northwestern University Feinberg School of Medicine in Chicago.
The study included 145 patients with mild or moderate illness within 1 week of symptom onset. The researchers used reverse transcriptase–polymerase chain reaction (rt-PCR) on nasopharyngeal swabs collected at inpatient, outpatient, emergency department, or drive-through testing sites to measure SARS-CoV-2 levels. The investigators compared PCR amplification cycle threshold (CT) values for children younger than 5 years (n = 46), children aged 5 to 17 years (n = 51), and adults aged 18 to 65 years (n = 48); lower CT values indicate higher amounts of viral nucleic acid.
Median CT values for older children and adults were similar (about 11), whereas the median CT value for young children was significantly lower (6.5). The differences between young children and adults “approximate a 10-fold to 100-fold greater amount of SARS-CoV-2 in the upper respiratory tract of young children,” the researchers write.
“Behavioral habits of young children and close quarters in school and day care settings raise concern for SARS-CoV-2 amplification in this population as public health restrictions are eased.”
Modeling the Impact of School Slosures
In the JAMA study, Katherine A. Auger, MD, of Cincinnati Children’s Hospital Medical Center, Ohio, and colleagues examined at the US population level whether closing schools, as all 50 states did in March, was associated with relative decreases in COVID-19 incidence and mortality.
To isolate the effect of school closures, the researchers used an interrupted time series analyses and included other state-level nonpharmaceutical interventions and variables in their regression models.
“Per week, the incidence was estimated to have been 39% of what it would have been had schools remained open,” Auger and colleagues write. “Extrapolating the absolute differences of 423.9 cases and 12.6 deaths per 100,000 to 322.2 million residents nationally suggests that school closure may have been associated with approximately 1.37 million fewer cases of COVID-19 over a 26-day period and 40,600 fewer deaths over a 16-day period; however, these figures do not account for uncertainty in the model assumptions and the resulting estimates.”
States that closed schools when the incidence of COVID-19 was low had the largest relative reductions in incidence and mortality, the authors found.
Decisions With High Stakes
In an accompanying editorial, Julie M. Donohue, PhD, and Elizabeth Miller, MD, PhD, both affiliated with the University of Pittsburgh, emphasized that the results are estimates. “School closures were enacted in close proximity…to other physical distancing measures, such as nonessential business closures and stay-at-home orders, making it difficult to disentangle the potential effect of each intervention,” they write.
Although the findings “suggest a role for school closures in virus mitigation, school and health officials must balance this with academic, health, and economic consequences,” Donohue and Miller add. “Given the strong connection between education, income, and life expectancy, school closures could have long-term deleterious consequences for child health, likely reaching into adulthood.” Schools provide “meals and nutrition, health care including behavioral health supports, physical activity, social interaction, supports for students with special education needs and disabilities, and other vital resources for healthy development,” they note.
In another viewpoint also published in JAMA, authors involved in the creation of a National Academies of Sciences, Engineering, and Medicine (NASEM) report on reopening schools described their recommendation that districts “make every effort to prioritize reopening with an emphasis on providing in-person instruction for students in kindergarten-grade 5 as well as those students with special needs who might be best served by in-person instruction.”
“To reopen safely, school districts are encouraged to ensure ventilation and air filtration, clean surfaces frequently, provide facilities for regular handwashing, and provide space for physical distancing,” write Kenne A. Dibner, PhD, of the NASEM in Washington, DC, and coauthors.
Furthermore, districts “need to consider transparent communication of the reality that while measures can be implemented to lower the risk of transmitting COVID-19 when schools reopen, there is no way to eliminate that risk entirely. It is critical to share both the risks and benefits of different scenarios,” they write.
The JAMA modeling study received funding from the Agency for Healthcare Research and Quality and the National Institutes of Health. The National Academies of Sciences, Engineering, and Medicine report was funded by the Brady Education Foundation and the Spencer Foundation. The authors had no conflict of interest disclosures.
JAMA Pediatrics. Published online July 30, 2020. Abstract