Epidemiology Unit, Agency for Health Protection of Milan, Milano, Italy.
Department of Sociology and Social Research, University of Milan-Bicocca, Milano, Italy.
PLoS One. 2022 Jul 12;17(7):e0271404. doi: 10.1371/journal.pone.0271404. eCollection 2022.
In February 2021, the spread of a new variant of SARS-CoV-2 in the Lombardy Region, Italy caused concerns about school-aged children as a source of contagion, leading local authorities to adopt an extraordinary school closure measure. This generated a debate about the usefulness of such an intervention in light of the trade-off between its related benefits and costs (e.g. delays in educational attainment, impact on children and families' psycho-physical well-being). This article analyses the epidemiological impact of the school closure intervention in the Milan metropolitan area.
Data from the Agency for Health Protection of the Metropolitan City of Milan allowed analysing the trend of contagion in different age classes before and after the intervention, adopting an interrupted times series design, providing a quasi-experimental counterfactual scenario. Segmented Poisson regression models of daily incident cases were performed separately for the 3-11-year-old, the 12-19-year-old, and the 20+-year-old age groups, examining the change in the contagion curves after the intervention, adjusting for time-varying confounders. Kaplan-Meier survival curves and Cox regression were used to assess the equality of survival curves in the three age groups before and after the intervention.
Net of time-varying confounders, the intervention produced a daily reduction of the risk of contagion by 4% in those aged 3-11 and 12-19 (IRR = 0·96) and by 3% in those aged 20 or more (IRR = 0·97). More importantly, there were differences in the temporal order of contagion decrease between the age groups, with the epidemic curve lowering first in the school-aged children directly affected by the intervention, and only subsequently in the adult population, which presumably indirectly benefitted from the reduction of contagion among children.
Though it was not possible to completely discern the effect of school closures from concurrent policy measures, a substantial decrease in the contagion curves was clearly detected after the intervention. The extent to which the slowdown of infections counterbalanced the social costs of the policy remains unclear.
2021 年 2 月，意大利伦巴第地区新型 SARS-CoV-2 变异株的传播引发了人们对学龄儿童作为传染源的担忧，导致当地政府采取了一项特别的学校关闭措施。这引发了一场关于这种干预措施是否有用的辩论，因为它涉及到相关收益和成本之间的权衡（例如，教育程度的延迟、对儿童和家庭心理-生理健康的影响）。本文分析了米兰大都市区学校关闭干预措施的流行病学影响。
米兰大都市卫生保护局的数据允许我们在干预前后分析不同年龄组的感染趋势，采用中断时间序列设计，提供准实验性的对照情景。对 3-11 岁、12-19 岁和 20 岁及以上三个年龄组分别进行每日新发病例的分段泊松回归模型，在校正时间变化混杂因素后，检查干预后的感染曲线变化。Kaplan-Meier 生存曲线和 Cox 回归用于评估干预前后三个年龄组生存曲线的均等性。
净时间变化混杂因素后，干预使 3-11 岁和 12-19 岁年龄组的感染风险每天降低 4%（IRR=0.96），20 岁及以上年龄组降低 3%（IRR=0.97）。更重要的是，三个年龄组的感染减少的时间顺序存在差异，受干预直接影响的学龄儿童的流行曲线首先降低，随后成年人口的流行曲线才降低，这可能是儿童感染减少带来的间接收益。
尽管我们无法完全区分学校关闭措施与同期政策措施的效果，但干预后明显检测到感染曲线的大幅下降。减缓感染的程度与政策的社会成本之间的平衡仍不清楚。
