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. 2021 Mar 13;160(2):529–537. doi: 10.1016/j.chest.2021.03.004

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© 2021 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

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SMRs. Using PIM2 with 95% CIs, reference line at 1 indicates that the number of observed deaths is equal to the number of expected deaths. PIM2 = Pediatric Index of Mortality-2; Q1 = quartile 1; Q2 = quartile 2; SMR = standardized mortality ratios.