IMR Press / FBL / Volume 27 / Issue 5 / DOI: 10.31083/j.fbl2705157
Open Access Review
The Potential Roles of BCG Vaccine in the Prevention or Treatment of COVID-19
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1 Tuberculosis Prevention and Control Key Laboratory/Beijing Key Laboratory of New Techniques of Tuberculosis Diagnosis and Treatment, Senior Department of Tuberculosis, The 8th Medical Center of PLA General Hospital, 100091 Beijing, China
2 Department of General Medicine, The 8th Medical Center of PLA General Hospital, 100091 Beijing, China
*Correspondence: (Wenping Gong); (Hongmei Wang)
These authors contributed equally.
Academic Editor: Sang Heui Seo
Front. Biosci. (Landmark Ed) 2022, 27(5), 157;
Submitted: 29 March 2022 | Revised: 18 April 2022 | Accepted: 22 April 2022 | Published: 13 May 2022
(This article belongs to the Special Issue Vaccine and anti-viral drug development for SARS-CoV2)
Copyright: © 2022 The Author(s). Published by IMR Press.
This is an open access article under the CC BY 4.0 license.

Coronavirus disease 2019 (COVID-19), which broke out at the end of 2019, is a global pandemic and seriously threatens human health. Vaccination is the most effective way to prevent and control COVID-19. At present, more than 13 COVID-19 vaccines have been urgently authorized for use, but the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants has brought unprecedented challenges to the protective efficiency of these COVID-19 vaccines. In particular, the recent emergence of Delta and Omicron variants, which are rapidly spreading worldwide, may bring many challenges to the medical systems. Interestingly, previous studies have shown that the Bacillus Calmette-Guerin (BCG) vaccine used to prevent tuberculosis can induce non-specific trained immunity, protecting against infectious diseases caused by respiratory viruses. Therefore, there is a hypothesis that BCG plays an essential role in reducing the incidence, severity, hospitalization, and mortality of COVID-19 and enhancing the protection efficiency of the COVID-19 vaccine. To confirm this hypothesis, 56 clinical trials have been conducted globally to assess BCG’s protective effectiveness against COVID-19 infection. Herein, this review discussed the trained immunity induced by BCG and its underlying mechanisms and summarised BCG’s latest research progress in preventing COVID-19, especially the ongoing clinical trials. We hope this review will provide new strategies for fighting against COVID-19.

Bacillus Calmette-Guerin (BCG)
trained immunity
Fig. 1.
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