The COVID-19 pandemic is one of the biggest health challenges faced by humanity in over a century. Unlike the 1918 Spanish influenza, data on the COVID-19 pandemic have been extensively collected, analysed, documented and monitored in real time by numerous organisations.1–4 Due to the scale of the pandemic and the variable success in tackling it in different countries, it is important to identify factors and policies affecting mortality, to retrospectively assess their effectiveness, and to help inform the response to any future pandemic. Although a large volume of work has been already done, this work will continue for many more years. Early in the pandemic, testing limitations often led to undercounting of COVID-19 deaths, particularly in countries with weaker health systems. This undercount varied across countries and changed over time as testing became more widespread. Therefore, the straightforward counting of the officially registered deaths from COVID-19 is problematic. Fortunately, in 2020, epidemiologists and demographers reached a consensus regarding the use of the excess mortality approach for the estimation of mortality due to COVID-19.5–7 This method, based on a comparison of expected (from historical trends) and observed mortalities, produces the most reliable estimates that are not biased by differences in testing and reporting practices. Excess mortality also helps to capture the full impact of the pandemic, including its wider effects on health systems, and allows assessment of the effectiveness of public health, economic and medical interventions.8 9 Despite a long history of estimating ‘excess deaths’ during wars and pandemic,10 and numerous methodological advances based on mathematical modelling in more recent decades, the main obstacle for accuracy of estimations before the COVID-19 pandemic was the limited availability of high-quality data. Estimates of excess deaths and death rates for the years 2020 …

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理解 COVID-19 大流行导致的死亡率过高的国家和国际差异

COVID-19 大流行是一个多世纪以来人类面临的最大健康挑战之一。与 1918 年西班牙流感不同，许多组织广泛收集、分析、记录和实时监测 COVID-19 大流行的数据。1-4 由于大流行的规模以及不同国家应对该流行病的成功程度各不相同，重要的是要确定影响死亡率的因素和政策，回顾性评估其有效性，并帮助为应对未来的任何大流行病提供信息。尽管已经完成了大量工作，但这项工作还将持续很多年。在大流行早期，检测限制往往导致对 COVID-19 死亡人数的低估，特别是在卫生系统较弱的国家。不同国家的漏报情况各不相同，并且随着测试变得更加广泛而随着时间的推移而变化。因此，直接统计官方登记的 COVID-19 死亡人数是有问题的。幸运的是，2020 年，流行病学家和人口统计学家就使用超额死亡率方法来估计 COVID-19.5-7 造成的死亡率达成了共识。这种方法基于预期死亡率（来自历史趋势）和观察到的死亡率的比较，得出最可靠的估计不会因测试和报告实践的差异而产生偏差。超额死亡率还有助于全面了解这一流行病的影响，包括其对卫生系统的更广泛影响，并可以评估公共卫生、经济和医疗干预措施的有效性。8 9 尽管估算战争期间“超额死亡”的历史由来已久10 以及近几十年来基于数学模型的众多方法论进步，在 COVID-19 大流行之前估计准确性的主要障碍是高质量数据的可用性有限。 2020 年超额死亡人数和死亡率估计……