This review highlights the convergence of three global health challenges at a crossroad where the pandemic of coronavirus disease 2019 (COVID-19) meets the tobacco epidemic and vaping. It begins with an overview of the current knowledge on the biology, pathophysiology and epidemiology of COVID-19. It then presents the state of smoking and vaping during the pandemic by summarizing the published data on prevalence, use patterns, product availability/accessibility, sales records and motivation to quit before and after the start of the pandemic. It highlights the state of evidence on the association of tobacco product use with COVID-19 infection and transmission rates, symptom severity and clinical outcomes. Also discussed are proposed biological mechanisms and behavioral factors that may modulate COVID-19 risk in tobacco product users. Furthermore, competing hypotheses on the protective effect of nicotine against COVID-19 as well as the claimed 'smokers' paradox' are discussed. Considerations and challenges of COVID-19 vaccination in tobacco product users are underscored. Collectively, the present data show an 'incomplete' but rapidly shaping picture on the association of tobacco product use and COVID-19 infection, disease course and clinical outcomes. Evidence is also growing on the mechanisms by which tobacco product use may contribute to COVID-19 pathophysiology. Although we await definitive conclusions on the relative risk of COVID-19 infection in tobacco product users, compelling data confirm that many comorbidities associated with/caused by smoking predispose to COVID-19 infection, severe disease and poor prognosis. Additionally, it is becoming increasing clear that should smokers get the disease, they are more likely to have serious health consequences.

中文翻译：

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COVID-19：一场大流行与全球烟草流行和广泛的电子烟证据相融合。

这篇综述强调了三个全球健康挑战在 2019 年冠状病毒病 (COVID-19) 大流行与烟草流行和电子烟的交汇处的融合。它首先概述了 COVID-19 的生物学、病理生理学和流行病学的当前知识。然后，它通过总结大流行开始前后有关流行率、使用模式、产品可用性/可及性、销售记录和戒烟动机的已发布数据，展示大流行期间吸烟和使用电子烟的状态。它强调了烟草产品使用与 COVID-19 感染和传播率、症状严重程度和临床结果之间关联的证据状态。还讨论了可能调节烟草制品使用者 COVID-19 风险的拟议生物机制和行为因素。此外，讨论了关于尼古丁对 COVID-19 保护作用的竞争假设以及声称的“吸烟者悖论”。强调了烟草产品使用者对 COVID-19 疫苗接种的考虑和挑战。总的来说，目前的数据显示了关于烟草产品使用与 COVID-19 感染、病程和临床结果之间关联的“不完整”但正在迅速形成的图景。关于烟草产品使用可能导致 COVID-19 病理生理学机制的证据也越来越多。尽管我们正在等待关于烟草产品使用者感染 COVID-19 的相对风险的明确结论，但令人信服的数据证实，许多与吸烟相关/由吸烟引起的合并症易患 COVID-19 感染、严重疾病和预后不良。此外，