First BCG vaccine is prepared from

(B) Mycobacterium bovis > Calmette and Guerin, two French scientists began attenuating a virulent strain of M. bovis in 1906, with a view to develop a vaccine against tuberculosis. After 230 subcultures over a period of 13 years, they were able to evolve a strain - known as bacille Calmette Guerin or BCG - which was avirulent for man while retaining its capacity to induce an immune response. Initially BCG was given orally during 1921 to 1925. The first human was vaccinated by the intradermal technique in 1927. Recognition of the value of BCG came in 1948 when it was accepted by tuberculosis workers from all over the world as a safe preventive measure.