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. 2021 Feb 22;49(6):694–700. doi: 10.1016/j.ajic.2021.02.012

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© 2021 The Authors

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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Study Flow Diagram of Search Results for Included Patients. A total of 4,549,598 unique patient charts were searched within the Michigan Medicine health care system using DataDirect. The search was limited to include only patients who received a laboratory test for COVID-19 within the Michigan Medicine healthcare system. Record of influenza vaccination between August 1, 2019 to July 15, 2020 was then obtained.