New modeling work from UMC Utrecht and collaborators argues that school closures during a pandemic are most effective when they are deliberately timed and targeted. Published in Nature Communications, the study links counterfactual school policies to the changing dynamics of viral spread, offering a framework for decisions when evidence is incomplete and timelines are tight.
The researchers built a mathematical model that reconstructs how SARS-CoV-2 moved through the Dutch population, explicitly incorporating contacts involving elementary and secondary schools during COVID-19. By combining epidemiological time series with transmission modeling, they simulated alternative closure and reopening strategies and assessed their downstream impact on severe outcomes, including hospital admissions.
A central finding is that the principal age groups driving transmission were not constant. Early in the pandemic, adults contributed the largest fraction of transmission. As immunity in older groups accumulated—through prior infection and vaccination—the relative role shifted toward teenagers.
By 2021, younger children became increasingly susceptible, reflecting broader immunity patterns in adults and adolescents. This epidemiological reweighting altered which school sector mattered most for epidemic control, changing the policy “lever” available to decision makers.
Consequently, closing secondary schools produced the strongest reductions in hospital admissions during 2020, aligning with the period when teenagers were dominant transmitters. Toward the end of 2021, the model indicates that closing elementary schools became more effective, consistent with rising transmission relevance among younger children.
Rather than endorsing a single uniform approach, the study supports adaptive intervention design: closures should evolve as susceptibility, contact patterns, and transmissibility shift across the outbreak trajectory.
The authors emphasize that computational models can improve preparedness by translating shifting transmission drivers into actionable guidance. In practice, targeted closures may reduce infections while limiting educational disruption relative to blanket measures.
They also plan to extend the model to evaluate broader consequences of school interventions, including impacts on children’s learning and development. Future work will explore how social and demographic differences modulate transmission, aiming to strengthen outbreak readiness across varied settings.
Subject of Research: People
Article Title: Counterfactual evaluation of elementary and secondary school policies in the COVID-19 pandemic
News Publication Date: 21-Jul-2026
Web References: http://dx.doi.org/10.1038/s41467-026-73344-1
References: 10.1038/s41467-026-73344-1
Image Credits: UMC Utrecht
Keywords: Viral transmission; COVID-19; school closures; mathematical modeling; epidemiology; computational simulation; age-specific susceptibility; public health policy; Nature Communications; SARS-CoV-2
