Smallpox was eradicated worldwide due to vaccination campaigns to wipe it out all over the globe. Pneumonia and influenza which used to kill people in huge numbers was greatly reduced. Due to the development of antibiotics and the use of vaccines in children during the 20th century, diseases like diptheria, tuberculosis, whooping cough and typhoid fever were greatly reduced. Polio was also greatly reduced because of childhood vaccine programs. A vaccine consists of a weakened or dead virus which is injected into a person. These foreign antigens trigger the immune response and the person produces antibodies. Now, if they come into contact with a live virus, the body will have developed an immunity to it. Anti-viral medicines are also available to treat diseases like H.I.V. However, the term greatly reduced does not mean a disease is cured. Also, because bacteria can pass on resistance genes to other bacteria and their offspring, people are constantly forced to create newer and more powerful antibiotics to fight resistant infections.