The BCG vaccine was first administered to humans in 1921 to protect against tuberculosis.
BCG stands for Bacillus Calmette–Guérin, named after French researchers Albert Calmette and Camille Guérin. They developed it from Mycobacterium bovis, a bacterium related to the organism that causes human tuberculosis. After repeated laboratory subculturing, the strain was weakened so it could stimulate immunity without causing tuberculosis.
The first human recipient was a newborn infant in Paris in 1921. The vaccine was given orally, unlike the intradermal injections commonly used today. BCG later became especially important for protecting children against severe forms of tuberculosis, including tuberculous meningitis and miliary tuberculosis.
Protection against adult pulmonary tuberculosis varies considerably between populations, so BCG does not eliminate the need for tuberculosis diagnosis, treatment, or public-health measures. It is also not a routine vaccine in every country. A common mix-up is confusing BCG with vaccines against diphtheria or pneumonia: BCG specifically targets tuberculosis and may leave a small characteristic scar after injection.