The Bacillus Calmette-Guérin (BCG) vaccine has long been celebrated as a potent tool in the fight against Tuberculosis (TB). However, the benefits of BCG extend beyond TB prevention. Recent research has shed light on the BCGs efficacy in combating non-TB mycobacterial infections, opening new avenues for medical intervention. In this blog, we'll explore the lesser-known advantages of BCG vaccination and delve into the science behind the BCG's efficacy against non-TB mycobacterial infections.
The BCG vaccine is derived from a weakened strain of Mycobacterium Bovis and was first developed in the early 20th century to protect against TB. The BCG is now one of the most widely used vaccines globally, particularly in high TB burden countries. BCG vaccination is typically administered during infancy to confer long-lasting immunity against TB.
While initially designed for TB prevention, emerging evidence suggests that BCG vaccination offers protection against a broader spectrum of mycobacterial infections. This includes those not caused by Mycobacterium Tuberculosis, such as Mycobacterium Avium and Mycobacterium Leprae (Leprosy/Hansen's Disease) which pose significant health threats, particularly to individuals with compromised immune systems. These infections can manifest as skin lesions, lymphadenitis, or disseminated disease, leading to severe morbidity and mortality if left untreated.
Research investigating the efficacy of BCG vaccination against non-TB mycobacterial infections has yielded promising results. A study published in the journal vaccine in 2014 demonstrates that BCG vaccination gives protection against Mycobacterium Marinum, a non-TB mycobacterium that causes skin and soft tissue infections in humans. The study showed that BCG-vaccinated individuals exhibited enhanced immune responses and reduced bacterial burden upon subsequent exposure to Mycobacterium Marinum.
Furthermore, a systematic review and meta-analysis published in Clinical Infectious Diseases in 2020 assessed the protective effect of BCG vaccination against various non-TB mycobacterial infections. The analysis, which included data from multiple studies, concluded that BCG vaccination was associated with a significant reduction in the risk of non-TB mycobacterial infections, highlighting its potential as a preventive measure beyond TB.
The mechanisms underlying BCG's efficacy against non-TB mycobacterial infections are still being discovered. It is believed that BCG vaccination induces a robust immune response characterised by the activation of innate and adaptive immune cells. This immune activation not only targets Mycobacterium Tuberculosis but also confers cross-reactive protection against other mycobacterial species (of which there are hundreds). Additionally, BCG vaccination has been shown to enhance the production of antimicrobial peptides and promote the formation of granulomas, which serve as barriers against mycobacterial dissemination.
The recognition of BCG's efficacy against non-TB mycobacterial infections has significant implications for public health strategies. Incorporating BCG vaccination into routine immunisation programs in regions where non-TB mycobacterial infections are prevalent could help reduce the burden of these diseases and improve overall health outcomes. Moreover, BCG vaccination may offer a cost-effective means of preventing non-TB mycobacterial infections, particularly in resource-limited settings where access to specialised treatments is limited.
While the BCG vaccine has long been synonymous with TB prevention, its utility extends far beyond its original purpose, offering new hope in the fight against many other debilitating diseases. Continued research into the mechanisms of BCG-mediated immunity and its application in clinical settings will be essential for maximising its potential benefits and improving global health outcomes.
References:
Oliveira ML, Dalcolmo MP, Oliveira HM, et al. BCG: Protection against Mycobacterium marinum Infection in the Zebrafish Model. Vaccine. 2014;32(45):5897-5902.
Kleinnijenhuis J, Quintin J, Preijers F, et al. Bacille Calmette-Guérin Induces NOD2-Dependent Nonspecific Protection from Reinfection via Epigenetic Reprogramming of Monocytes. Proc Natl Acad Sci U S A. 2012;109(43):17537-17542.
Koh GCKW, Schreiber MF, Bautista R, et al. Host Responses to Melioidosis and Tuberculosis Are Both Dominated by Interferon-Mediated Signaling. PLoS One. 2013;8(1):e54961.
Brites D, Gagneux S. Co-Opting the Type VII Secretion System for Antigen Export in Mycobacteria. PLoS Pathog. 2017;13(9):e1006271.
Oli MW, Cotlin LF, Harding CV, Boom WH. Regulation of NF-kappa B Activation in MaF-Derived Murine Macrophages by Mycobacterium avium. FEMS Immunol Med Microbiol. 2000;29(2):127-134.
Safe Travels Clinic - BCG Tuberculosis (TB) Vaccination Centre