The article "The potential preventive role of a dietary supplement containing hydroxytyrosol in COVID-19: a multi-center study", by K. Dhuli, C. Micheletti, M.C. Medori, G. Madeo, G. Bonetti, K. Donato, F. Gaffuri, G.M. Tartaglia, S. Michelini, A. Fiorentino, D. Cesarz, S.T. Connelly, N. Capodicasa, M. Bertelli, published in Eur Rev Med Pharmacol Sci 2023; 27 (6 Suppl): 33-38-DOI: 10.26355/eurrev_202312_34687-PMID: 38112946 has been retracted by the Editor in Chief for the following reasons. Following some concerns raised on PubPeer, the Editor in Chief has started an investigation to assess the validity of the results. The outcome of the investigation revealed that the manuscript presented major flaws in the following: - Issues with ethical approval - Issues in methodology - Undeclared conflict of interest Consequently, the Editor in Chief mistrusts the results presented and has decided to withdraw the article. The authors disagree with this retraction. https://www.europeanreview.org/article/34687 This article has been retracted. The Publisher apologizes for any inconvenience this may cause.