CalmetteGuerin

CalmetteGuerin, more commonly known as Bacillus Calmette-Guérin (BCG), is a live attenuated strain of Mycobacterium bovis used for medical purposes. It was developed by French researchers Albert Calmette and Camille Guérin at the Pasteur Institute in the early 20th century. After years of subculturing, the strain was attenuated to reduce virulence while preserving immunogenicity. BCG was first used in humans in the 1920s and is now part of many national immunization programs as a vaccine against tuberculosis, especially for children.

The protective effect of BCG against pulmonary tuberculosis in adults is variable and depends on geography, prior exposure to environmental mycobacteria, and the specific vaccine substrain used. However, it is consistently effective at preventing severe forms of TB in children, such as miliary TB and meningitis. Administration is by intradermal injection, and vaccine strains differ among countries, which can influence efficacy and interpretation of tuberculin skin tests. Safety is generally good but contraindicated in individuals with severe immunodeficiency, active tuberculosis, or certain medical conditions; adverse effects include local ulceration, lymphadenitis, and, rarely, disseminated BCG infection.

In addition to vaccination, BCG is used as an intravesical immunotherapy for non-muscle invasive bladder cancer. It is instilled directly into the bladder to stimulate an immune response that helps prevent tumor recurrence. Common side effects resemble cystitis and, rarely, systemic infection. BCG therapy has become a standard treatment option in urologic oncology.