According to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic literature search was performed in May 2020 and included all reports published to August 2020. The search was performed on specialized databases (PubMed and Scopus) using different combinations of HCQ and the following keywords: history, discovery, ethnomedical, synthesis, chemical structure, SAR, RAS, biological activity, approved biological activities, antiviral, antiviral mechanism, COVID-19, Q fever, Whipple’s disease, synergistic effects, synergic effects, toxicological effects, toxic effects, toxicity, animal model and antiviral activity, clinical study, preclinical study. We did not request full-text to investigators if not available and we did not try to find unpublished data.