What is the purpose of the BCG vaccine?

• A. It is a killed vaccine given to infants
• B. It prevents TB across all populations
• C. It treats active TB
• D. It is a live, attenuated strain of Mycobacterium bovis given to infants in areas with high TB prevalence

Answer: (D)

The Vaccine works by priming the immune system to fight TB, especially to prevent severe TB in children. It uses a live, attenuated strain of Mycobacterium bovis, which creates a robust cell-mediated immune response that helps protect against serious TB forms like meningitis and disseminated disease in early life. It is typically given to infants in areas where TB is common, because the risk of severe TB in children is higher there and the vaccine’s benefit is greatest in that group. It is not a treatment for active TB and does not reliably prevent pulmonary TB in adults. It is not a killed vaccine, and protection is not universal across all populations, which is why its use is targeted to high-prevalence settings.