BCG: a vaccine with multiple faces

Abstract

BCG has been recommended because of its efficacy against disseminated and meningeal tuberculosis. The BCG vaccine has other mechanisms of action besides tuberculosis protection, with immunomodulatory properties that are now being discovered. Reports have shown a significant protective effect against leprosy. Randomized controlled trials suggest that BCG vaccine has beneficial heterologous (nonspecific) effects on mortality in some developing countries. BCG immunotherapy is considered the gold standard adjuvant treatment for non-muscle-invasive bladder cancer. BCG vaccine has also been tested as treatment for diabetes and multiple sclerosis. Erythema of the BCG site is recognized as a clinical clue in Kawasaki disease. BCG administration in the immunodeficient patient is associated with local BCG disease (BCGitis) or disseminated BCG disease (BCGosis) with fatal consequences. BCG administration has been associated with the development of autoimmunity. We present a brief review of the diverse facets of the vaccine, with the discovery of its new modes of action providing new perspectives on this old, multifaceted and controversial vaccine.

The non-specific and sex-differential effects of vaccines

“…In high-income countries, several studies from Europe and the USA suggest that admission to hospital for unrelated infections may be reduced by live measles vaccine and BCG vaccine but increased by non-live DTP vaccine 9,10 . Evidence from high-income countries also indicates that BCG vaccination may reduce the severity of allergy 11 , malignancy [12][13][14] , diabetes 15 and Alzheimer disease 16,17 .…”

Bacillus Calmette Guérin (BCG) Vaccination use in the Fight Against COVID-19 – What's Old is New Again?

“…Since introduction of the BCG vaccine in 1921, an increasing body of evidence has demonstrated its ability to exert a range of nonspecific immunological effects beneficial for a range of other conditions. In epidemiological studies, neonatal BCG vaccination is associated with reduction in all-cause child mortality by 30% (0.70; CI 95%, 0.49-1.01), widely thought to be related to reduction in rates of neonatal sepsis and pneumonia [3]. BCG has the ability to train the innate immune system to generate an immune memory against secondary infections, a process also termed trained immunity [4].…”

Active Pulmonary Tuberculosis Triggered by Interferon Beta-1b Therapy of Multiple Sclerosis: Four Case Reports and a Literature Review

“…This could be an opportunity to find more effective vaccines in the fight against tuberculosis [20]. However, the protection lasts for only five to ten years after vaccination and therefore, scientists are looking for ways to improve and increase the vaccine's efficiency [21,22]. We can speculate that IFNβ-1b therapy may impair protective immunity to Mycobacterium tuberculosis, given the complex immune mechanisms and genetic determinants of the two conditions.…”