Consider the question. Tuberculosis (TB) vaccines are vaccinations intended for the prevention of tuberculosis. Immunotherapy as a defence against TB was first proposed in 1890 by Robert Koch. Today, the only effective tuberculosis vaccine in common use is bacilli Calmette-Guerin (BCG), first used in 1921. About three out of every 10,000 people who get the vaccine experience side effects, which are usually minor except in severely immuno-depressed individuals. While BCG immunization provides fairly effective protection for infants and young children, (including defence against TB meningitis and miliary TB), its efficacy in adults is variable, ranging from 0 % to 80 %. Several variables have been considered as responsible for the varying outcomes. Demand for TB immunotherapy advancement exists because the disease has become increasingly drug-resistant.

Answer this question based on the passage: what is the name of the vaccine for tuberculosis?
What is the step-by-step reasoning process to arrive at the answer: Calmette - Guerin ( BCG )?
To answer the above question, the relevant sentence is: Today, the only effective tuberculosis vaccine in common use is bacilli Calmette-Guerin (BCG), first used in 1921.