Explanation:

BCG, or bacille Calmette-Guerin, is a vaccine for tuberculosis (TB) disease.

• BCG is used in many countries with a high prevalence of TB to prevent childhood tuberculous meningitis and miliary disease.
• Currently, BCG is the only licensed vaccine available for the prevention of TB.
• In children, BCG provides strong protection against severe forms of TB. This protective effect is far more variable in adolescents and adults, ranging from 0–80%.

Hence option 4th is correct.