Immunization (vaccination) is a method of increasing the human immune system against certain disease by using microorganisms, such as bacteria or virus, that have been modified or weakened. The microorganisms become a trigger of immune system to build a defense mechanism which continuously protects the body from disease.
Scientists develop two immunization approaches, namely active immunization which gives long term immunity and passive immunization which give temporary immunity.
Active immunization is conducted by injecting vaccine containing specific antigen into the body to build immune system. Antigen is a substance found in pathogen antigen which is recognized by the immune system as foreign particles.
As a response to antigen, the immune system will develop antibody or T lymphocyte of white blood cell which is a special attacker cell. Some immunizations give complete protection against particular diseases for a life time. Another type is by giving partial protection, it means the person given immunization only gets temporary immunity. Some other type of immunization require repetition injection periodically, for example tetanus injection which is suggested to be injection once in every 10 years of a life time.
Active immunization uses modified organism so that it will reduce the risk of causing disease. But it is still able to build a defense system to fight disease, such as to protect the body from yellow fever, measles, chickenpox, and many other diseases caused by virus.
Immunization may also occurs when someone receives an injection containing inactivated or killed microorganism, so that it is relatively safe, but it still contains antigen, i.e. polio, typhus, and diphtheria.
Several vaccines only use antigenic part of cell, such as protein, wall cell, and flagellum. This kind of vaccine is known as acellular vaccine is used for whooping cough.
Passive immunization is conducted without injecting any antigen. In this method, vaccine contains antibody that is obtained from animal or human blood who actively immunized. The antibody can protect some one from specific disease only for two to three weeks. Even though it has a short life, but this immunization gives immediate or faster protection, i.e. for canned food poisonous and rabies case.