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Review
. 2021 Jun;361(6):683-689.
doi: 10.1016/j.amjms.2021.03.003. Epub 2021 Mar 8.

Bacillus Calmette-Guerin Vaccine and Nonspecific Immunity

Kanak Parmar  1 , Afzal Siddiqui  1 , Kenneth Nugent  2
Affiliations
Review

Bacillus Calmette-Guerin Vaccine and Nonspecific Immunity

Kanak Parmar et al. Am J Med Sci. 2021 Jun.

Abstract

Bacillus Calmette-Guerin (BCG) vaccine is one of the most widely used vaccines in the world. It protects against many non-mycobacterial infections secondary to its nonspecific immune effects. The mechanism for these effects includes modification of innate and adaptive immunity. The alteration in innate immunity is through histone modifications and epigenetic reprogramming of monocytes to develop an inflammatory phenotype, a process called "trained immunity." The memory T cells of adaptive immunity are also responsible for resistance against secondary infections after administration of BCG vaccine, a process called "heterologous immunity." Bacillus Calmette-Guerin vaccine is known to not only boosts immune responses to many vaccines when they are co-administered but also decrease severity of these infections when used alone. The BCG vaccine by itself induces a TH1 type response, and its use as a vector has also shown promising results. This review article summarizes the studies showing effects of BCG vaccines on various viral infections, its role in enhancing vaccine responses, the mechanisms for this protective effect, and information on its effect on COVID-19.

Keywords: Bacillus Calmette-Guerin vaccine; Heterologous immunity; Influenza; Recombinant BCG vaccine; Trained immunity; Viral infections.

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Conflict of interest statement

Conflict of interest statement The author has no financial or other conflicts of interest to disclose.

Figures

Fig 1
Fig. 1
This figure outlines the possible changes in immunity following Bacillus Calmette-Guerin (BCG) vaccination.
See this image and copyright information in PMC

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