Importance In the US, states enacted nonpharmaceutical interventions, including school closure, to reduce the spread of coronavirus disease 2019 (COVID-19). All 50 states closed schools in March 2020 despite uncertainty if school closure would be effective. Objective To determine if school closure and its timing were associated with decreased COVID-19 incidence and mortality. Design, Setting, and Participants US population-based observational study conducted between March 9, 2020, and May 7, 2020, using interrupted time series analyses incorporating a lag period to allow for potential policy-associated changes to occur. To isolate the association of school closure with outcomes, state-level nonpharmaceutical interventions and attributes were included in negative binomial regression models. States were examined in quartiles based on state-level COVID-19 cumulative incidence per 100 000 residents at the time of school closure. Models were used to derive the estimated absolute differences between schools that closed and schools that remained open as well as the number of cases and deaths if states had closed schools when the cumulative incidence of COVID-19 was in the lowest quartile compared with the highest quartile. Exposures Closure of primary and secondary schools. Main Outcomes and Measures COVID-19 daily incidence and mortality per 100 000 residents. Results COVID-19 cumulative incidence in states at the time of school closure ranged from 0 to 14.75 cases per 100 000 population. School closure was associated with a significant decline in the incidence of COVID-19 (adjusted relative change per week, -62% [95% CI, -71% to -49%]) and mortality (adjusted relative change per week, -58% [95% CI, -68% to -46%]). Both of these associations were largest in states with low cumulative incidence of COVID-19 at the time of school closure. For example, states with the lowest incidence of COVID-19 had a -72% (95% CI, -79% to -62%) relative change in incidence compared with -49% (95% CI, -62% to -33%) for those states with the highest cumulative incidence. In a model derived from this analysis, it was estimated that closing schools when the cumulative incidence of COVID-19 was in the lowest quartile compared with the highest quartile was associated with 128.7 fewer cases per 100 000 population over 26 days and with 1.5 fewer deaths per 100 000 population over 16 days. Conclusions and Relevance Between March 9, 2020, and May 7, 2020, school closure in the US was temporally associated with decreased COVID-19 incidence and mortality; states that closed schools earlier, when cumulative incidence of COVID-19 was low, had the largest relative reduction in incidence and mortality. However, it remains possible that some of the reduction may have been related to other concurrent nonpharmaceutical interventions.

中文翻译：

---

美国全州学校停课与 COVID-19 发病率和死亡率之间的关联


重要性 在美国，各州颁布了包括关闭学校在内的非药物干预措施，以减少 2019 年冠状病毒病 (COVID-19) 的传播。尽管学校关闭是否有效尚不确定，但所有 50 个州均于 2020 年 3 月关闭了学校。目的 确定学校停课及其时间是否与 COVID-19 发病率和死亡率下降有关。设计、设置和参与者 美国基于人群的观察性研究于 2020 年 3 月 9 日至 2020 年 5 月 7 日期间进行，使用包含滞后期的中断时间序列分析，以允许发生潜在的政策相关变化。为了分离学校停课与结果的关联，负二项式回归模型中纳入了州级非药物干预措施和属性。根据学校关闭时每 10 万居民中州级 COVID-19 累积发病率，对各州进行了四分位数检查。使用模型得出关闭学校和保持开放学校之间的估计绝对差异，以及当 COVID-19 累计发病率处于最低四分位数与最高四分位数相比时，如果各州关闭学校，病例数和死亡人数。风险 中小学停课。主要成果和措施 每 10 万居民中的 COVID-19 每日发病率和死亡率。结果 学校关闭时各州的 COVID-19 累积发病率范围为每 10 万人中有 0 至 14.75 例病例。学校关闭与 COVID-19 发病率（每周调整后相对变化，-62% [95% CI，-71% 至 -49%]）和死亡率（每周调整后相对变化，-58）显着下降相关。 % [95% CI，-68% 至 -46%]）。 这两个关联在学校关闭时 COVID-19 累积发病率较低的州中规模最大。例如，COVID-19 发病率最低的州的发病率相对变化为 -72%（95% CI，-79% 至 -62%），而相对变化为 -49%（95% CI，-62% 至 -33）。 %）针对累积发病率最高的州。在该分析得出的模型中，据估计，当 COVID-19 累积发病率处于最低四分位数与最高四分位相比时关闭学校，与 26 天内每 10 万人中病例减少 128.7 例以及死亡人数减少 1.5 例相关。 16 天内每 100 000 人。结论和相关性 2020 年 3 月 9 日至 2020 年 5 月 7 日期间，美国学校停课暂时与 COVID-19 发病率和死亡率下降相关；在 COVID-19 累积发病率较低时较早关闭学校的州，发病率和死亡率的相对下降幅度最大。然而，部分减少仍然可能与其他同时进行的非药物干预措施有关。