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Regular COVID-19 Screening in Schools Can Control Infections, Limit Closures

The model suggests screening unvaccinated students could reduce absences by 80% compared to reactively closing classes with infected students.

The coronavirus disease 2019 (COVID-19) pandemic prompted schools worldwide to cancel in-person learning for weeks and months, but a new study argues schools can—and should—safely operate with a mix of vaccination and regular testing of unvaccinated students.

The study, published in The Lancet Infectious Diseases, is based on a model of school transmission developed based on contact data and pilot screenings from 683 French schools.

Corresponding author Vittoria Colizza, PhD, of Sorbonne University, said the experience of the pandemic has made 2 things clear: having schools open leads to an increase in community transmission and yet keeping schools open should be a “primary objective” to safeguard the educational, emotional, and social needs of children.

Assessing vaccination and protocols in schools is therefore key to maintaining schools open in light of a continuously evolving pandemic,” Colizza and colleagues said.

Using data from 2 periods in 2021, the authors created a model that could be used to see how various interventions might affect transmission and risk in a school setting. The authors calculated school-specific reproductive numbers for COVID-19 for both the Alpha and Delta variants.

For the Alpha variant, the reproductive number was 1.40 (95% confidence interval [CI] 1.35-1.45) in the primary school and 1.46 (95% CI 1.41-1.51) in secondary schools. They noted that that rate was higher than the rate estimated via community surveillance.

For the Delta variant, they found something of a divergence, with a significantly higher reproductive number in primary schools, 1.66 (95% CI 1.60-1.71), and a lower reproductive number in secondary schools, 1.10 (95% CI 1.06-1.14).

Using those rates, the investigators calculated that if the schools tested 75% of unvaccinated students on a weekly basis and tested any student with symptoms, they could reduce cases by 34% in primary schools and 36% in secondary schools.

Moreover, such a regime would translate into fewer lost days of instruction. In fact, the authors said such a strategy could reduce lost days by 80% compared to simply testing symptomatic children and then closing their classes.

“Our analysis indicates that regularly screening the school population is efficient in preventing infections while reducing absence from school, especially in settings where the school population is not yet vaccinated, coverage is low to moderate, or vaccine protection has largely waned,” Colizza and colleagues wrote.

The investigators said even with masks and other precautions, transmission is likely at schools. They said their model affirms that a regular testing protocol is a critical component of viral mitigation at school.

“It also provides a cost-benefit analysis considering successive variants, comparing multiple protocols, and evaluating the key role of adherence in the context of partly vaccinated school populations,” they wrote.

Notably, while the authors said their goal was to limit both community spread and missed days of school, they said it is not clear that reactive classroom closures are even particularly effective, given that the virus can spread silently, and some people do not have obvious symptoms. They said proactive screening allows school officials to detect more cases, enabling them to take a more targeted approach when deciding which students need to isolate.

Colizza and colleagues emphasized that vaccinating students is essential. While vaccination of teachers is beneficial, the authors said it does not significantly limit spread, even if a school’s entire teaching staff is vaccinated.

“This results from the small number of teachers and the observed lower rate of interaction they have with students, and it is confirmed even when community incidence in adults is much higher than in the student-age classes,” they wrote.

The authors concluded that COVID-19 is likely to continue to be a factor affecting public health and education for the foreseeable future.

“​​Regular testing remains a key strategy to epidemic control in school settings with moderate vaccination coverage or following waned vaccine protection, all the while minimizing days lost,” they concluded.