BCG vaccination involves administering an attenuated strain of Mycobacterium bovis to induce artificial primary infection and increase immune response against tuberculosis. It has been shown to reduce mortality from TB by 71% and risk of infection by 51% according to case control studies. Effectiveness can vary based on factors like exposure, vaccine strain, age administered, and recipient nutrition status. Common side effects include local ulceration and lymphadenitis in 1-10% of cases. Chemoprophylaxis with isoniazid is an alternative but not widely used in India due to cost and compliance issues.