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Fiction and Facts about BCG Imparting Trained Immunity against COVID-19

Immunology Laboratory, Department of Biomedical Engineering, Indian Institute of Technology Ropar, Rupnagar 140001, India
Immunology Laboratory, Division of Cell Biology and Immunology, CSIR-Institute of Microbial Technology, Chandigarh 160036, India
Author to whom correspondence should be addressed.
Academic Editors: Rafael Blasco, Javier Ortego and Alejandro Marin-Lopez
Vaccines 2022, 10(7), 1006;
Received: 22 May 2022 / Revised: 17 June 2022 / Accepted: 21 June 2022 / Published: 23 June 2022
(This article belongs to the Special Issue COVID-19 Vaccine Candidate Development)
The Bacille Calmette-Guérin or BCG vaccine, the only vaccine available against Mycobacterium tuberculosis can induce a marked Th1 polarization of T-cells, characterized by the antigen-specific secretion of IFN-γ and enhanced antiviral response. A number of studies have supported the concept of protection by non-specific boosting of immunity by BCG and other microbes. BCG is a well-known example of a trained immunity inducer since it imparts ‘non-specific heterologous’ immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus responsible for the recent pandemic. SARS-CoV-2 continues to inflict an unabated surge in morbidity and mortality around the world. There is an urgent need to devise and develop alternate strategies to bolster host immunity against the coronavirus disease of 2019 (COVID-19) and its continuously emerging variants. Several vaccines have been developed recently against COVID-19, but the data on their protective efficacy remains doubtful. Therefore, urgent strategies are required to enhance system immunity to adequately defend against newly emerging infections. The concept of trained immunity may play a cardinal role in protection against COVID-19. The ability of trained immunity-based vaccines is to promote heterologous immune responses beyond their specific antigens, which may notably help in defending against an emergency situation such as COVID-19 when the protective ability of vaccines is suspicious. A growing body of evidence points towards the beneficial non-specific boosting of immune responses by BCG or other microbes, which may protect against COVID-19. Clinical trials are underway to consider the efficacy of BCG vaccination against SARS-CoV-2 on healthcare workers and the elderly population. In this review, we will discuss the role of BCG in eliciting trained immunity and the possible limitations and challenges in controlling COVID-19 and future pandemics.
Keywords: Innate immunity; BCG; SARS-CoV-2; COVID-19; vaccines Innate immunity; BCG; SARS-CoV-2; COVID-19; vaccines
MDPI and ACS Style

Kaur, G.; Singh, S.; Nanda, S.; Zafar, M.A.; Malik, J.A.; Arshi, M.U.; Lamba, T.; Agrewala, J.N. Fiction and Facts about BCG Imparting Trained Immunity against COVID-19. Vaccines 2022, 10, 1006.

AMA Style

Kaur G, Singh S, Nanda S, Zafar MA, Malik JA, Arshi MU, Lamba T, Agrewala JN. Fiction and Facts about BCG Imparting Trained Immunity against COVID-19. Vaccines. 2022; 10(7):1006.

Chicago/Turabian Style

Kaur, Gurpreet, Sanpreet Singh, Sidhanta Nanda, Mohammad Adeel Zafar, Jonaid Ahmad Malik, Mohammad Umar Arshi, Taruna Lamba, and Javed Naim Agrewala. 2022. "Fiction and Facts about BCG Imparting Trained Immunity against COVID-19" Vaccines 10, no. 7: 1006.

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