What purpose this BCG vaccines are used?

The BCG vaccine (Bacillus Calmette-Guérin) is primarily used to prevent severe forms of tuberculosis (TB), such as meningitis and disseminated TB, in newborns, infants, and young children.

It is a live attenuated vaccine, meaning that it contains a weakened strain of the bacterium that causes tuberculosis (Mycobacterium bovis). When the vaccine is administered, the body's immune system responds by producing antibodies and immune cells specifically targeted against the TB bacteria.

The BCG vaccine is particularly important in regions where TB is common or where there is a high risk of exposure to the disease. While it does not provide complete protection against all forms of TB, studies have demonstrated its effectiveness in preventing severe and disseminated forms of the disease, especially in children.

It's worth noting that the BCG vaccine is not widely used in all countries, and its administration and recommended age for vaccination can vary depending on the local epidemiology and healthcare policies.