The BCG vaccine, or Bacillus Calmette-Guérin vaccine, is primarily used to protect against tuberculosis (TB). It is made from a weakened strain of the bacterium that causes TB and is administered through an injection. The vaccine is most effective in preventing severe forms of TB, especially in children. In many countries, the BCG vaccine is part of routine childhood immunizations. While it does not guarantee complete protection against TB, it significantly reduces the risk of severe disease and complications. The vaccine is particularly important in areas where TB is common, helping to control the spread of this infectious disease.