(a) BCG - BCG (Bacillus Calmette Guerin) is a vaccine that is used to treat Tuberculosis (TB) which is a bacterial disease as it develops immunity to TB. (b) Incubation period - It is the period between the entrance of the germs and the appearance of the first symptoms of the disease. Incubation period of Tetanus of 4-20 days. (c) Chicken pox - It is caused by the Herpes Varicella zoster virus and is a viral disease. It rapidly spreads through close contact with the person infected. (d) Hepatitis A - It is caused by the Hepatitis A virus and is a viral disease that results in liver inflammation. It is transferred primarily through contaminated water and food.