CalmetteGuérin

Calmette-Guérin, commonly abbreviated as BCG, is a live attenuated vaccine derived from Mycobacterium bovis. It is named after French scientists Albert Calmette and Camille Guérin, who developed the strain at the Pasteur Institute in Lille and first used it in humans in 1921. The vaccine is designed to stimulate cell-mediated immunity and is primarily used to protect against tuberculosis, particularly severe and disseminated disease in children, though protection against adult pulmonary tuberculosis varies by setting and time since vaccination.

BCG vaccines are administered intradermally, typically to newborns or young children in countries with high tuberculosis prevalence; vaccination policies in low-incidence regions vary. Efficacy against pulmonary tuberculosis in adults is variable and influenced by exposure, geography, and vaccine strain differences, but BCG remains effective against tuberculous meningitis and miliary tuberculosis in children.

In addition to vaccination, Calmette-Guérin is used as an intravesical therapy for non-muscle invasive bladder cancer. Instillation of live BCG into the bladder invokes a local immune response that can reduce tumor recurrence and progression in selected patients, often following transurethral resection of the tumor.

Safety and contraindications: as a live vaccine, BCG is generally contraindicated in individuals with significant immunosuppression (for example, HIV infection with AIDS or immunosuppressive therapy) and in those with active tuberculosis or disseminated infection. Common adverse effects include injection-site reactions and low-grade fever; disseminated BCG infection is rare but serious.

Other notes: BCG strains have diverged into several substrains worldwide, contributing to geographic differences in vaccine properties. BCG remains the only widely used vaccine for TB prevention and a cornerstone of bladder cancer immunotherapy.