Effect of BCG on Respiratory Complications Caused by COVID-19: A Scoping Review

Cristiane Giacomelli da Costa,1,* Mehrsa Jalalizadeh,1,* Reza Yadollahvandmiandoab,1 Keini Buosi,1 Leonardo O Reis1,2 1Department of UroScience, School of Medical Sciences, University of Campinas – UNICAMP, Campinas, São Paulo, Brazil; 2Pontifical Catholic University of Campinas, PUC, Campinas, São Paulo, Brazil*These authors contributed equally to this workCorrespondence: Leonardo O Reis, Department of UroScience, School of Medical Sciences, University of Campinas, UNICAMP, Campinas, São Paulo, Brazil, Tel +55 19 35217481, Email Reisleo@unicamp.brIntroduction: Bacillus Calmette–Guérin (BCG) has been shown to have protective effects against respiratory viruses. We conducted a scoping review of the literature to clarify the available evidence regarding the effect of BCG therapy in preventing respiratory complications of coronavirus disease 2019 (COVID-19).Methods: We searched PubMed, Embase, CENTRAL, Scopus, and Web of Science for related studies up to October 2022.Results: In total, 35 publications and trials were included. One animal study, two observational studies, and six finalized trials measured the effect of BCG administration on respiratory complications of COVID-19. The remaining publications included eight unfinished trials, 12 ecological studies, and six observational studies that did not directly measure respiratory complications but assessed overall mortality of the disease and were included as an adjunct to our study. All trials involved vaccinating adults to protect them against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, and measured respiratory symptoms or the need for intensive respiratory support as the primary or secondary aim of the study. One trial that exclusively included at-risk adults between 18 and 60 years old showed a decreased chance of respiratory complications as the secondary outcome of the study. Another trial that exclusively evaluated this effect on the elderly (60 years