Although anti-TPO IgG benignly occurs in around 10% of the healthy population48, our discovery of new-onset antithyroid antibodies emerging with mild to severe COVID-19 is concerning given that large epidemiological studies have shown increased incidence of autoimmune and autoinflammatory disorders, including autoimmune thyroid diseases, following COVID-1949,50. Here, TPO is linked to autoimmune thyroid disease.