Abstract: International Journal of Antimicrobial Agents 56 (2020) 106118 Contents lists available at ScienceDirect International Journal of Antimicrobial Agents journal homepage: www.elsevier.com/locate/ijantimicag Lactoferrin as potential preventative and adjunct treatment for COVID-19 Raymond Chang a,∗, Tzi Bun Ng b, Wei-Zen Sun a,c a Institute of East–West Medicine, 102 E 30th Street, New York, NY 10016, USA Chinese University of Hong Kong, Shatin, N.T., Hong Kong c National Taiwan University Hospital, 7 Chung Shan S. Road., Taipei, Taiwan b a r t i c l e Keywords: Lactoferrin COVID-19 SARS-CoV-2 Antiviral Viral prophylaxis i n f o a b s t r a c t The coronavirus disease 2019 (COVID-19) pandemic is rapidly advancing across the globe despite drastic public and personal health measures. Antivirals and nutritional supplements have been proposed as potentially useful against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the novel coronavirus that causes COVID-19, but few have been clinically established. Lactoferrin (Lf) is a naturally occurring, non-toxic glycoprotein that is orally available as a nutritional supplement and has established in vitro antiviral efficacy against a wide range of viruses, including SARS-CoV, a closely related coronavirus to SARS-CoV-2. Furthermore, Lf possesses unique immunomodulatory and anti-inflammatory effects that may be especially relevant to the pathophysiology of severe COVID-19 cases. Here we review the underlying biological mechanisms of Lf as an antiviral and immune regulator, and propose its unique potential as a preventative and adjunct treatment for COVID-19. We hope that further research and development of Lf nutritional supplementation would establish its role for COVID-19. © 2020 Elsevier Ltd and International Society of Antimicrobial Chemotherapy. All rights reserved.