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. 2021 Nov 18;15(1):13–20. doi: 10.1016/j.jiph.2021.11.012

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© 2021 The Author(s)

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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Fig. 1 — The flowchart showing the strategy of participants’ enrollment.

Abbreviations: CVD, cardiovascular diseases (except hypertension); RSD, respiratory system disease; IC, immunocompromised conditions; CMD, chronic metabolic diseases (except diabetes); GDC, gastrointestinal and digestive comorbidities.

^aOther diseases: rheumatism and autoimmune diseases (55), blood disorders (51), Mental disorders (47), Neurological diseases (41), others that cannot be classified but affect the health of the patients (46, such as history of headache, dizziness, fever of unknown cause, etc.).